My advice runs contrary to Robin's. If an employer pays for your flight, you will be commited, either by your own sense of honor and/or duty, or by a contract. I've read here the advice of others who agree with Robin about this, but from my own experience and that of others I feel much more comfortable about paying my own way and checking out the whole scene thoroughly before making a commitment. If I don't like it, I can move on and with my tourist visa in hand I can seek out a suitable position.
Now having said that, I would agree that if the employer sends you pictures and well documented proof of the schools willingness to hire you and care for you properly - visas and etc., then go for it. But the pictures should clearly show you the apartment you will live in (inside and out), the computer you will be given to use, the school and if possible one of the classrooms.It wouldn't hurt to request some recent photos of the neighborhood and city you will be living in.
Remember though, if they attempt to lure you by glowing descriptions of the city you will work in and how great the school is and they refuse to provide you with documentation and pictures, you are probably being scammed. Many teachers have ended up in garbage heap cities and rat infested apartments while counting the days until their contract expires while teaching unappreciative, non-motivated students in non-heated or air conditioned classrooms. And oh yes, there may be up to 70 students in those classrooms and you'll be lucky if 10% are attentive or interested enough to make you feel like your efforts are at least partially appreciated.
I've been here for three years now and I'm happy to say that I enjoy it. I enjoy my students generally and I've learned to find the right schools or universities to teach at. But I've had to pay my dues. Thus my advice to others here in this forum. Just because I suffered through it, doesn't mean I want others to.
Take the time to do your RESEARCH!