Spinning mill or feasible? Buy and renovate an old farmhouse

50-60,000€: For what exactly? You write that it is in great need of renovation. That means also roof, facade, windows, doors. Heating, electricity, connections, water pipes, and a complete interior fit-out with plaster, floors, ceilings, walls, interior doors, stairs, and bathrooms? If yes: Then I say no, that’s rather not enough. And then it is also a major project that you can’t do alone in a few months alongside work. Please first write more precisely what needs to be done, how big the house is, and simply more details.

We partially renovated our 100m2 terraced house from 1921 (roof, facade, front door, and heating system were still in good condition: we renovated electricity, bathrooms, ceilings, walls, floors, stairs, interior doors, water pipes, and partially radiators and windows, roof insulation inside and roof windows). We did most of it ourselves and have so far estimated to have spent about 60,000€, maybe also 70,000€ - I don’t know exactly because quite a bit was also spent in the garden. All normal medium standard, no luxury. Electricity, some plumbing, tiling work, and roof insulation were done by professionals.

I don't find Lumpi's cost breakdown unrealistic at all. For example, the topic of windows: Sure, pure windows are cheap, but if you want a front door, large sliding door to the garden, new windowsills, and electric shutters installed, you quickly reach around €20,000 for the "windows" item. If you want to keep the old building charm with drafty huge shutter boxes inside, it will be cheaper. A new building is usually calculated here at €2000/m². That means you can easily expect well over €1000/m² for a major renovation. Anecdotal individual cases of how cheaply you could do it yourself unfortunately don't help anyone here. Because if you can manage that, you ask your craftsman buddies and not us here.

but the house is in need of extensive renovation, [...] and there is only a stove heating system.

When a layperson recognizes "in need of extensive renovation," it is often just the tip of the iceberg. And the age of the technology (not the exact year of construction/installation, but rather: in which decade the current state was) is roughly equivalent to the "beginning of the renovation backlog era" of the property. This also applies, in a similar sense, to aesthetic aspects: when the wallpaper was modern gives a clue as to when the walls were last broken open, i.e., to the age of cables and wiring. In terms of the maintenance of properties and equipment, agriculture, the postal service, and the railway are no different. The year of decommissioning allows an estimate of whether a repair is still worthwhile: thirty years of elapsed time correspond as a rough guideline to one hundred percent decay.

Lumpi, my offer stands! Let me know when you go shopping!

Yes.. blah blah without wanting to rant at you now. Now a quick word about the heating: according to the OP, there are stoves here that must be removed and disposed of, that’s expensive, if you even find someone who does it. An old farmhouse will hardly have a gas connection, so the only sensible option is a heat pump, and for such an old house not a small one. Additionally, there is a heat distribution network, standard is underfloor heating and that comes with a lot. For that crap to actually work someone should plan it, no one does that for free either. Heat pump and underfloor heating don’t cost less than 30k even in new buildings.. Of course you can also put a basic stove in the living room, costs about 10,000 all in. Have fun the next few years.

And since you’re so keenly interested. I built my heating myself and it didn’t cost anywhere near 50,000 or 30,000, but the OP probably won’t be able to do that based on his question.

If there is no gas, you use oil and radiators.
Rolled shutters in an old farmhouse? A complete style break.
There are probably very small wooden muntin windows in there, replacing them with plastic ones doesn't cost tens of thousands.
I stick to the fact that you can get very far with 60 for materials.

Heat pump and underfloor heating are not done under 30k in new buildings..

From the craftsman? Then yes, but I thought this is about self-performance? Our air-to-water heat pump including underfloor heating in a new building for 156 sqm = just under 18k in self-performance, pump from Weishaupt.