First of all be very careful when choosing an estate agent. You may ask your friends or do your own research. I bought my house in Avren this summer through HouseBulgaria. They are very friendly people, answered all my questions and helped me at every stage of the buying process. They are really very nice guys (this is of course my own opinion). You can visit their website. When buying in Bulgaria foreigners have to open a Bulgarian company on behalf of which the property is bought. The initial capital is 5000 leva, or at least 3500 leva which you put in a bank account and refund after the company is ready. Usually the estate agent helps with the company set up.

i pm-ed you a link you can search the large database of properties listed there by different estate agents good luck with your research