I opened my first school in 2003 in Latin America . I had a Tefl certification from a good school in Thailand. That really helped on the teaching side of things and designing my own curriculum. Build your own program and perfect it based on the issues students have locally. Generic books are boring. You will have to balance learning with dynamic classes to keep students in their seats. If you do nothing but grammar all day, they will leave because they can do that in local schools with teachers that can't pronounce the words. High focus on speaking and pronunciation is popular in Latin America, especially with native speakers.
The business side I had no idea what I was doing, here's a few tips I learned:
-Start small with low overhead. One room classroom with small reception area. You can always grow into a bigger school. But it will help while you build your reputation and word of mouth.
-Tourist towns are not ideal because the economy fluctuates with high and low seasons (probably already has 50 schools) . Transient population that tends to be more flaky students. Many only work during the high tourist season then go home for low season. Yes, they are pretty and what probably drew you to the country initially but they have always underperformed compared to my other schools and prices are higher. Down the road, you will appreciate not living there as you fully immerse into the "real" culture.
-Look for a strong local economy which can vary town to town (ie. Tech. International Corp.,agriculture, or within an hour or two of a major tourist area etc..). Or simply follow Wal-Mart (major company) that used a team of professionals to do the social economic data for you.
-If you're not a native speaker consider contracting teachers as it is much more desirable and sets you apart.
-Check local law for taxes, business licenses, visas, and being affiliated with local education dept.
-Be prepared to advertise online, flyers, and/or a radio ad blitz on a popular station.
-Look at local schools to see how they charge to save on printing for books, shop around and make a deal with a local school supply store. Copies are never ending. Ie. Inscripciones to pay for books.
-Find out high times to open. For example one country every August, January, and June tons of new students sign up. In between that, a trickle. So if you have your school open for business prior to the high sign-up, you may make enough to not only support the school but yourself comfortably the first year. Expect a good 3 years before you have a reputation strong enough, that you don't need to advertise anymore unless you're running a summer deal or during high sign-up times.
-Be prepared to screw up and make mistakes, run into licensing, immigration, tax issues. Competitors can get very petty and/jealous as you grow.
-Teachers can be very flaky. Many are there to learn the language and travel. Teaching is secondary, but they will never admit it. Some simply can't handle the cultural change for a sustainable amount of time.
There's a lot more, but enjoy the ride of learning, living, and owning your own business in another country.