For those looking for a simple answer, I went ahead and polled everyone I knew in the English teaching game, and the overwhelming majority of people, when pressed for a simple "yes" or "no" answer said you shouldn't move to Taiwan to teach English.
Let's look at why you shouldn't come, and for whom Taiwan is actually a good fit.
Can I make and save money teaching English in Taiwan?
Yes, you will be able to make and save money while you are working in Taiwan. If you work the minimum 14 hours for an Alien Resident Card (ARC) at the minimum industry pay of 500NT, your total income is 28,000 NT a month, or 336,000 NT a year. If you're government certified you can become a public or private school teacher for an average starting salary of 75,000 NT a month, usually tax free, paid for a full year, plus two paid months off for summer if you want it.
28,000 NT a month is really, really bad pay, but you can save money while you work here. On average I'd say an after school teacher is currently making only 35,000 a month. You won't be living the high life and can probably get more money by staying home or going elsewhere.
If you just want to make money go to China. Highest pay and lowest cost of living in East Asia. Use a reputable recruiter to avoid scams and you can save a lot more than other places. Korea and Japan also pay better and provide better benefits than in Taiwan, even to first time teachers who aren't certified.
Will teaching in Taiwan get me experience for a job back home?
This is especially important for Canadians or people from US states like New York. If you're getting real classroom hours at a proper school, complete with an English speaking reference, yes you will be getting teaching experience you can use towards applying for education jobs back home. If you're doing the after school program / buxiban thing, your experience is likely going to be of little use outside of getting a new teaching job in Taiwan. So if you are licensed to teach but can't get a job at home, Taiwan isn't a bad place to get some experience. For the record, Korean, China, and Japan all pay better than Taiwan and generally carry more weight experience wise back home.
Can I learn Chinese while I teach in Taiwan?
Yes, you could technically learn Chinese while you teach in Taiwan. If you will not be staying for at least two years, the language learning experience will likely be frustrating, incomplete, and in the end a total waste of your time and money. At upwards of 20,000NT for classes covering basic dialogue that slot in around your work it'd take you about three years to cover enough to even approach using Mandarin for anything outside of talking about family and your hobbies.
If you want to learn Chinese, don't come to Taiwan to work.
Your best bet is to go to China, specifically a class 2 or 3 city, and take language courses and maybe teach if you've got the time. Everyone in Taiwan speaks English outside of very rural areas where they speak Taiwanese, not Mandarin. In China you'll be pushed to actually use Mandarin to do everything while you could live in Taiwan for years and never speak a word. If you insist on coming to Taiwan you should apply for a scholarship from the government and sign up for an intensive language course. It should run at least half a day, five days a week, in a genuine classroom setting with homework and tests you can actually fail. Reports are the program at National Taiwan University gets people to fluency in about two years.
Do teachers have a bad reputation?
Generally, yes. Few people will say it to your face but teachers are basically seen as being failures in their own country who come to Taiwan to make easy money for doing nothing at work. Given the way most teachers behave, their level of understanding of the English language, and their entitled approach to what is an entirely isolated foreigner bubble universe, the local folks are right.
If you work at a real school, you're a bit older, not married, can't speak Chinese, etc., most people will start to think you're just not qualified to get a job back at home. Because let's be honest, if you become a lifer and don't engage your environment, you probably aren't qualified for a good job back home.
Will I make contacts or be able to find non-teaching jobs once I'm in Taiwan?
No. People will generally treat you as a good companion for partying or going out, but won't trust you enough to bring you into a business thing. That's even true for other foreign people living here. If you do get an offer, you'll need a master's degree or two years of verifiable, post-university experience in your job's field to qualify to get a visa. If you have an APRC and no experience, you'll get paid 30,000NT a month to do entry level work, 40 to 60 hours a week. If you make the minimum for foreigners of 50,000NT a month, you'll be working such long hours it'll still be about 200NT an hour.
You're better off trying to make your living from scanning beaches with a metal detector than you are trying to find a good office job in Taiwan. It can be done, but rarely happens.
Should I find a job before I arrive or set one up once I'm already there?
Using a third-party recruiter is the generally accepted method for teachers to get to Taiwan. Only advice is make sure they're reputable, don't agree to ever pay them any money out of your own paycheck, and read everything before you sign it. Getting 600 NT an hour for at least 20 hours a week is pretty standard. After your first year you can try to change schools if you want.
If you've got no experience teaching English in Taiwan, don't try to get a job on your own. The average posting gets over 200 responses, all of them qualified native speakers, and the selection is basically random. There are far, far more "English teachers" than there are positions. If you don't have at least three years of experience in Taiwan, and don't know how to network with a school's manager, you'll find it VERY difficult to work with a good school. FYI, most schools which post wanted ads outside of January or August are not good places to work, which is why they need a new teacher.
What is the standard hourly pay for teaching?
Pay generally hovers around 600NT an hour, although some schools will push you as low as 500. Schools which have exacting standards, managerial competence and oversight, and no tolerance for lazy, arrogant, or incompetent teachers will pay as high as 850 an hour. Taking a teaching job on contract outside of a genuine school is likely a bad idea. Work is generally the main focus of life here, so signing a blank check for monthly hours and salary to your boss is a bad, bad call. You will likely end up making just over 200NT an hour, or less.
Unless you're a public school teacher, it's normal to get deductions for tax and health insurance. Taxes can be withheld at a flat 18% every month if your school is lazy with their accounting, or as little as 0% which means you'll have to pay out of pocket eventually. Average actual tax is about 5% to 10%, but public school teachers get paid TAX FREE! You are eligible for tax returns which can be filed in May of the following calendar year, or should be filed before you exit the country if you leave your job in the middle of the year.
What happens if I quit my job before my contract expires?
If you quit before your contract expires you'll have to file a termination agreement with the government, extend or cancel your ARC, and eventually leave Taiwan. This depends a lot on what country you are from and what the current rules are for Taiwanese immigration. It's best to call the foreigner help line or contact your local immigration office.
Can my boss really take my money if I quit early?
Generally, so long as they follow procedure, yes. Labor law in Taiwan does not seem straightforward to most foreigners, and there is a lot of room for interpretation and compromise. Nearly every employment contract in Taiwan, be it for teaching or otherwise, has a clause in it that requires you to pay money to your employer if you leave. Office gigs call it a training and administration fee, running upwards of a few months pay. In teaching it's most likely going to be one month's pay or a 20,000NT flat fee.
Once you sign your contract, whatever punishment was there is usually enforceable. So yes, you can sign the majority of your labor rights away so long as it doesn't pose physical danger, etc. The only time you can try to get out the punishment stuff is if the conditions outlined for repayment weren't met. Generally this means the training you're compensating them for wasn't provided to you, or the company broke the terms of your contract first. It is illegal for a company to withhold your pay, but that's the most likely the company will get your money.
If you get into trouble or reach a serious impasse with your boss you need to file a mediation or pay a lawyer for a lawsuit. Any dispute over your contract or payment is best handled in out of court third party mediation that is legally binding, does not require a lawyer, is done entirely in Mandarin, is face to face with your boss, and for most people is incredibly stressful.
Definitely consult one of the government's free lawyers if you have questions. Translators are always available!
Is it easy to party and travel around Asia while teaching English in Taiwan?
Yes, but it depends on your boss. Not all schools provide for full holidays during long government weekends. For example, during the four day tomb sweeping holiday, three day dragon boat festival, etc., many teachers will need to work at least one of the weekend mornings. It's also when everyone in Taiwan takes their family for quick trips around the region, so you're paying more for tickets, packing into full airplanes with unhappy families, and generally putting yourself in the way of peak season travel. Chinese New Year is a mess, and there are sometime weekend hours there as well.
If you work together with your boss and arrange a random weekend where someone can fill in for you and there are cheap airline tickets, it's easy to make your own long weekend! If you're at a real school it'll cut into your vacation days, and if you do after school programs it just eats those hours off your pay. It's totally worth it to travel to Thailand or somewhere for 1300NT in airfare round trip though, right?
Taiwan's party scene has started to mature and change in a lot of ways after a fire in Taichung, a stabbing in Taipei, and a lot of arrests island wide in the last few years. Don't believe everything you've read online about the club, party or pick up scene in Taiwan.
If you're at a public or private school with real hours and expectations you'll likely only be able to stomach the energy to get out and party on Saturday nights. Hooray for hung over Sundays before heading back to work for 7am Monday!
If you're an after school teacher your schedule likely starts after lunch time. Enough time to sober up, get that hangover fixed up, and head to work. There is at least some form of party 7 days a week - although some mid-week clubs are anti-foreigner - where you can go and drink yourself silly and bring shame to foreign people island wide.
Here's a quick thought for the bros: If you're coming to Taiwan to be a sociopathic sex predator, you should NOT believe that all Taiwanese girls are easy, and the strong consensus about foreign guys is they're dirty, dangerous, and just looking for one nighters. Try somewhere in Southeast Asia if you're trying to pick up on the regular.
For anyone looking to party: Truth be told, all the people who are down for good times head to Australia on working holidays, get it out of their system, and come back to find a job and get hitched. If you're trying to pick up Taiwanese people or just be where Asian 20 somethings are looking for awesome times, Australia is still probably the best place to do it right now. You probably qualify for a working holiday visa yourself, and the pay is often double - or higher - what it is in Taiwan.
Taiwan is good if you're looking to make below industry average money to teach English and have no real hope at a meaningful career. The best candidates for this are actually people joining family here. Otherwise, it's a good place for you to have a balanced life between work and play while figuring stuff out after college. Do one year in Taiwan and then move on to a new country in the region. Definitely travel around here as much as you can, learn as much about the local lifestyle as you can, and don't be a drunken mess who makes everyone feel worse about themselves.