I was in the same circumstances as you 10 years ago. I bought a house as an investment and a place to retire to. I paid 12K euro for a village house near Dobrich, it suits me as it is 35-40 minutes from the nearest coast and has many different resorts all within an hour, plus the road to Silistra and the Danube is good quality and a pleasant drive. However my house was burgled while left empty but luckily it was all the furniture and wood burner that came with the house, the house was then left with broken door locks for a few years. My circumstances changed and I went to live in Africa for a few years.
I returned to Bulgaria June 2015, for a holiday and booked hotels in many places for a six week tour. I stopped in Dodrich for 4 nights and visited my house, a gypsy woman from the village had moved her clothes in and was squatting. She was pleased to see me and told me she was my "Security" but she had burnt out the wiring and could I rewire it for her!!
My wife liked the country so while we were visiting Sofia we decided to go back and rewire the house and make it habitable for us to return and live in while refurbishing it. I rewired the house and laid a wood floor in the bedroom and connected a toilet in the bedroom for later constructing an en suite and had two new upvc doors fitted. I then went to the Mayor (Kmet) with the gypsy woman and explained I was giving permission for her to have the key to my house and until I return she is officially my security and anything damaged or missing she will be responsible. That worked well as when I returned in February 2016 the place was as I had left it. She hadn't even used my new toilet but used the outside latrine.
My roof looks OK for another 5 years so I didn't replace it but I removed the chimney's, never seen lead flashing available her so they put cement around the chimney and roof tiles, if you look at chimney's as you tour around you will see they all leak and most are falling down. Mine dismantled without tools as it is only mud and brick. I have fitted a stainless steel chimney out through the back wall, it cost me 700lev but was worth it. My house is four rooms all 16sqM and my wood burner gives out 15KW. We like the heat especially my wife who is Ugandan and even when it dropped to minus 22 our lounge was never below 27. in fact I wore tee shirts all through the winter. In summer it gets very hot but not very humid which is good for my arthritis.
I have now completed the internals and with buying everything (We arrived with just some clothes as we have left our house in Uganda furnished) we have spent £4,000 on a car and £16,000 on the house. Our further costs this year will be reconstructing the garage and the patio.
If you leave a property empty insure the building and contents. Arrange a security company (Сoд) there are many around. for a reasonable fee they will fit metal shutters over doors and windows which are alarmed back to their headquarters. They say that as soon as the shutter is interfered with the alarm goes off and a guard with dog will arrive before the burglar gets in. Alternatively another Englishman who leaves his house empty in my village has given a key to the neighbour and pays him a small monthly salary as security and gardener, also the windows need opening in good weather to air the place.
Hope this helps.