When buying second home in Bulgaria, be extremely careful when signing any preliminary agreements. Be sure to check when the property ownership will be transferred, at what moment exactly. The builders usually prefer that they get rid of the apartment/house at the moment of obtaining Act 15.
Act 14 This protocol (minutes) is to be drafted by the builder when the construction works of the building reach the so called "rough construction" or shell construction.
Act 15 is actually a protocol (minutes) signed by the investor, the builder, the architect and the private audit construction company. This protocol is to certify that the building is finished (not suitable for living though) and all the construction works are actually conformed to the approved architectural plan. However Act 15 doesn't allow you to legally inhabit the premises. Act 15 is an act of formal delivery of the building by the builder to the investor. Developers usually try to sell premises at the stage of Act 15. You shouldn't agree on that. But if you do, prepare to have trouble obtaining Act 16 (Habitation certificate" or "certificate for living suitability") i.e. collecting all the necessary documents.
Act 16 or"habitation certificate" is the formal certificate issued by the municipality audit commission. The latter checks if all the documents conform to the Bulgarian construction legislation as well as if the building is properly connected to the electricity, sewerage and water suppler. It checks if the premises are secure and suitable for living. You have to mind Act 16 when buying property in Bulgaria.