@Tony Wheeler
Wells/Boreholes
I reckon the majority of village houses have a well in the garden. Yours might be still working, or you might be able to get it working without too much trouble.
I'm not super convinced they are necessary, Bulgaria has very cheap mains water (9 euros for the last 2 months in our apartment). But all my neighbours have them, and they use them to irrigate the garden with free water. I doubt any of them are registered.
However, old wells are quite shallow (and hence may not very reliable with hotter summers / lower water tables). Almost everyone in my village has upgraded their well using modern technology (it's easy as my neighbour is the Drill Master), which costs a grand or two (this neighbour is doing very well, indeed).
In some places the water is very good (especially up in the mountains like us), so I'd guess you wouldn't have to do much to make sure it's safe to drink. However, again, I would take my lead from my neighbours, who are mostly using it as free irrigation water, rather than drinking water. The mains water is very good (at our village and in Plovdiv), I've been drinking 2-3 liters of the stuff daily for the last 6 years... and still haven't developed any radioactive spidey powers. :-)
I've lost electricity often (thunderstorms knock it out in the village), but I've lost water only once or twice, and that was for pipe repairs in the street for a couple of hours. So having it for emergency back-up would seem to be of limited utility. But if you want to be off-grid, that's a different story.
Our house has a well too, but it's a shallow one. Getting my neighbour in to drill a deep one remains on my to-do list. This one doesn't work because the last owner hacked it around to feed the swimming pool (ooh, fancy), and didn't finish the job. He also hacked around at the mains water so there was a tap to bypass the water meter when he needed to fill the pool or irrigate the garden. This is free water without any of the hassle of digging a well. :-) Of course, as a stupid foreigner, I saw this and had visions of the water police clapping me in irons and marching me off to water thieves jail, so I removed it immediately! But nobody has visited the meter in the 5 years I've owned it (they read it remotely, I don't know how, as it's definitely not a smart meter).
Septic Tank
There's not a lot of mains sewerage in Bulgarian villages, so most houses have a septic tank. It's a fairly traditional construction of a reinforced hole in the ground, sometimes with a run-off. Mine is stone and concrete, the run-off goes about 30m outside the house. My septic is still in use (must be 40+ years old), and works fine (as long as you don't flush paper). I've emptied it once, and it was very cheap.
Our village Mayor installed sewers in the streets about 7 or 8 years ago (before my time). I couldn't go uphill to the front, but I found an access cover at the backside of the house, but about 250m downhill. Two years ago we diggered a trench and buried a pipe, no hassles at all. It should work, but it goes to the septic, and I need to empty it again so that we can do the final connection.
I would personally just do what my neighbours are happy to do. But if you prefer to install a modern digestor-type septic, that's even better. But it will be more expensive, and may need electricity connected.
In both cases, I don't know what the regulations/laws say. But my (strong) impression is that most village folks get away with doing pretty much whatever they feel like doing. It's very laissez-faire here.