OK, that's a very broad question. Let me give the details:
We own a very old (estimate: about 100 years) rural house with some land. My wife spent lots of her childhood summers there, our kids like it, sentimental value, etc. We generally like the place, but the house is in a terrible shape.
It would probably need to have MAJOR renovations/upgrades done; or possibly even be rebuilt from scratch -- but we don't have that kind of finances available right now. We're not broke though - despite the COVID situation we're pretty financially stable and could devote some money to it. It's hard however for me to put down a specific number; and anyway the prices of things in my country (Latvia) cannot be directly compared to other countries, so I won't bother. Let's say I can afford small stuff (for a house). I would also like to complete the project myself without hiring additional people, unless absolutely necessary.
The house itself is a log-cabin type, although probably larger than what most people would imagine with that name. 3 large and 2 small rooms; a kitchen; spacious attic - it's a decently sized small house. I don't know the state of the logs themselves because they're covered both inside and out; but I'll assume they're fine. In the olden days people lived in the house all year long, but for decades now it has only been used as a summer cottage. Hence it is not being kept warm and dry all year round.
As far as we can tell, the house is built directly on the ground. There's no basement, and I doubt there are any supports in the ground or whatever. This also means that... the floors are directly on the ground too. As in, a most of the rooms have wooden floors which are more or less fine; but some just have thick, painted cardboard (there's probably a special name in English for cardboard that is meant for floors, but I don't know it). This cardboard... has not fared so well. In fact, the state of the floor in those rooms is pretty critical.
So, my current wish would be to restore that floor. Maybe even upgrade the floors in the other rooms too, if it seems worth it. But what do I do? Where do I start? What's the proper method that would ensure a structure that would last for ages?
Should I dig a pit beneath and add ventilation and sheets of plastic for moisture insulation? Pour concrete? A layer of bricks? Get creative with waterproofing membranes (the ones used in bathrooms)? I need ideas to work upon. :)