1. You won't get rich.
Of course, you knew that anyway. If you were looking for money, you would have chosen another career. Be prepared for the reality that teachers don't make a lot of money overseas. Depending on the job location, you may get housing included. Most likely you will have to find housing yourself. You definitely will not have a lot of money for luxuries. Just the bare necessities. If you are not frugal or don't want to learn how to be frugal, you need to confront that issue before you sign up. Otherwise, you will be miserable. If your spouse or partner is transferred outside the United States, then you have some breathing-room for finding a position. Perhaps your spouse's firm can open a few doors for you and point you in the right direction when it comes to finding employment.
2. Be open-minded.
Living abroad can take you outside of your comfort zone. After all, a country such as Bulgaria is not the United States. and that, frankly, is part of its charm. You won't find the foods which you are accustomed to. The living accommodations may not have some of the amenities to which you have grown accustomed. They do things differently over there. But, that's the point. Try new things. Experiment. It's an adventure.
3. Third world countries do not have first world amenities.
The electricity service may not be reliable. Snail mail is slow when it works at all. Cellphone service is usually fairly good because that infrastructure is new. Internet cafes abound but wifi is not generally available. Secondary and tertiary roads can be well-maintained or full of potholes and ruts.
4. Curricula will be different from those taught in the U.S.
If you are teaching in a state school, you will run into the gamut of required subjects and methods. In most cases, there is little room for improvisation. You must follow all the directives to the letter. Private schools will usually stick to the IB curriculum. If they have an expat clientele, they might even offer a British or American curriculum. It depends on the country.
"What may be okay in a Western classroom may not fly in a classroom in a non-Western country. I learned this the hard way. In Japan and many other Asian countries, students are not accustomed to putting their hands up to ask or answer questions. These countries tend to emphasize group culture and students hate to be singled out because they don’t want to seem more or less intelligent than their peers. Instead, I learned to break the ice in the classroom by using pair work, which made my students more comfortable and more likely to share their answers with everyone else.
Realization: combining your intelligence + adapting to the cultural learning needs of students = winning!"
5. Remember that you are a guest.
The reasons why you go abroad to teach are the same now as they were yesterday. You want to experience different cultures. You enjoy teaching and unleashing the creativity and imagination in young minds. Go for it.