Here you have many options, there are internet sites specialising in Bulgarian property and any     search engine will find you plenty.  Check out these sites for example :

Property sites

http://www.bulgarianproperties.com

http://www.imot.bg

http://www.imotibg.com/en/index.php

http://www.bg-properties.co.uk/

 http://www.orvitex.com - Orvitex

http://www.address.bg/ - Address

http://www.adis.bg/en/ - Adis

There are also many indigenous estate agents such as Orvitex, Address and Adis which are happy to deal with foreigners and take you through the steps. However, one peculiarity is that once a property is listed with one estate agent, they pass on the information to the others so that you really only need to go to one. They split the profits. They will arrange notaries (of which more later), transfer of money, hotels, transport etc.

These are the steps recommended for buying a property

Reserve a property by paying a deposit normally about 10-15% of the purchase price which you can do in person or even online or by post.
 Determine whether the sale is with land.
 If the sale is with land a company needs to be incorporated to hold the land.
 If sale is without land no company is needed.
 Your receive an initial contract of sale (similar to 'Sold subject to contract' in the UK).
 If already built, do the standard checks on the property using a reputable Bulgarian solicitor.
 Sign the Notary Act (Contract of purchase) in front of a Bulgarian Notary either in Bulgaria or at the Bulgarian embassy in London.
Please note that the final Notary Act is not signed until the building is completed in the case off plan developments.

Facts to consider when buying property in Bulgaria

The usual term for the old owners of the property to move out of it after completion of the sale is one month. This could be negotiated if the buyers require a shorter term. People should not expect the property to be empty right after signing of the final contarct.

All foreign buyers purchasing real estate property must be aware that in Bulgaria there are such terms as "tax estimation price" and "purchase price". The "tax estimation price" or municipality valuation is for the purposes of real estate taxation and is much lower than the actual selling (purchase) price.
Most of the Bulgarian property owners (vendors) wish that the "tax estimation price" is written in the title deed, and not the selling (asking) price which the buyers are paying, so due to this practice there might be discrepancies between the price you are paying and the price written in the title deed. This is because of various reasons. If the property buyer wishes that the purchasing price is written in the property title deed they must notify the estate agent  in advance and they will usually negotiate on this with the vendor of the property.  But be wary that if you insist on the full price as the municipality valuation of the property you could be asked for more or the owner could decide not to sell to you, both of which have happened to the author.