Renovation costs

Which interest rate is meant?

The 300 €! - is a giveaway ;) How do you get to 71000 from that? o_O

The 300 are actually a giveaway. The 71,000 are based on the standard land value of the municipality but are already 10€ below that. So the offer is good too - but I would rather invest the 71,000 in a veranda or something like that - what happens in 48 years doesn't matter to me for now. By then we will probably have to move into a nursing home anyway or can buy the property later.

At €300 per year and still 48 years validity, there isn’t even a hint of consideration at a purchase price of €71,000. The €300 is probably without regular increases and is already 52 years old; back then, 600 marks were still quite a lot. You can clearly see how little 600 marks/€300 are worth after 50 years.

What are you actually supposed to pay the family now? The value of the property or what was the appraiser even there for? The market is currently optimal for sellers, but run-down houses have never really been in demand. Sure, there is a buyer, but definitely not at the house’s value price. The 48 years of ground lease at €300/year is nice, but for a young couple, it is a few years too short (one would have to consider the purchase or a significantly more expensive new lease during retirement).
Such a house only really makes sense if you can initially do the rough work with a manageable budget and then do the rest yourself while already living in it.

There have already been enough interested parties from the family environment, I think on the open market the house with the (very awesome) plot should go for 100,000+. We would take the appraised 80,000 and save the property transfer tax.

I would actually describe us as a young couple (both still under 30), but I still see 48 years as a reasonable period. By the time that is up, we will be almost 80 – who knows what the world will look like then... The landowner wants to sell (an impoverished estate), so I also see good chances of buying it in 10 years.

It would be great for us that with 250,000 we could put together a great house and then have free scope for further investments for many years. We could actually live in it from the first interior construction steps (the usual) and then gradually, for example, finish converting the attic or similar.

We have found that certain tasks during renovation should not be postponed. These include the electrical system, water pipes, heating system including radiators, and the bathrooms. Additionally, the windows and the front door should be reviewed! Smaller tasks such as wallpapering and laying floor coverings in rooms that are not immediately needed can be postponed. The other tasks tend to be repeatedly delayed after moving in.

I also see good chances of buying that in 10 years.

It would be great for us to build a fantastic house with 250,000.

You probably don’t believe that when you have invested 250k, the land will be thrown at you afterwards. I would play hardball as the owner if you come in 10 years.
I have the ground lease anyway.