Bought a house cheaply. What now?

Now show me some photos!

And tell me something about the situation.
Unfortunately, it sounds a bit like a rough outback to me. (My interpretation based on the lonely auction date with the presence of the mayor)

I have to fully agree with nordanney there. Around the Düsseldorfe4 area, cheap properties rarely come on the market. But when they do, they’re usually old houses with an abandoned pub inside. Those are even slow sellers here.
Especially in the outback.
So I don’t believe in the illusion of reselling the property directly for a profit.

If you renovate the house so that you would move in yourself, it will be converted into a single-family house, right?
If the demand for that generally exists in the town, I would renovate with the option of moving in myself and watch the market.
If you have completed the change of use and already made some improvements with your own effort, I can well imagine that you can make a good profit.
Otherwise, just live in it yourself.

To buy a plot of land contaminated with a building, "only" at the price of the bare land, is already a real knee-slapper par excellence, but then to top it off with a vacant gastronomy space inside is even better. Here's to a Dujardin, then I guess I "have to" go to bed now, this day can hardly be improved any further. Thanks for the bedtime treat for amusement!
So all that's left for me is to quote the late Uli Wickert: the weather.

Buying such an object and—own statement—without any experience is, in my opinion, an absolute harakiri action, ...

I would like to point out that we do not know from many forum members (unless they have filled out the questionnaire) whether the purchase amount is "play money." It may be that some forum members, for whatever reasons, currently have a lot of money left over. It is probably an absolute minority, but they exist.

Whether your friend has now naively bought a house (or not) and whether that is smart (or not) is absolutely out of place in this thread and does not change the situation. Tips like "My advice to you is to just leave it as it is. If he, as you say, likes to take risks (in this case pure gambling) he should do that alone. You will most likely be very glad someday that you never signed anything under that." you should learn to ignore in this forum. No one who does not know you very well personally can judge that over the internet - such things only you can decide for yourself.

I think your question cannot be answered without further information. Whether to live in it yourself (if you even want to) depends on your financial situation and your current living situation. You should ask yourselves whether you can afford the renovation financially and whether you can imagine yourselves living in the renovated house afterward. Everything is possible, the question is only how much time and money it will cost. Otherwise: If you can/want to rent it out and at the end of the month come out a bit ahead every month, that’s also okay. In the very worst case, you just bought a plot of land. When reselling, you have to consider capital gains tax etc. First, it should be checked whether that would even be worthwhile or whether you will end up losing money.

The conversion (change of use from commercial to residential required) usually costs a lot of money.

This is interesting information. I have often wondered why the two former restaurants in our town were not converted into residential space. Basically, the conditions are often good; location in the town center, large, professional kitchen, and the former dining room as a beautiful, large open space. Thanks for the info.

Now, show some photos!

I agree, I would also like to see photos.