Land available - how to use it?

Then let's just do the math to get an idea of whether it's worth it.
270 sqm living area at €2,200 = €600K + €100K for additional construction costs etc. = €700K costs
270 sqm living area at €10 cold rent (should easily be possible even in a small town) = €34K including parking spaces per year.
So it's almost a 5% gross yield. You can do well with that, even as a real estate novice.

You forgot the land value, which accordingly reduces the yield.

What is the current standard land value? Or better: what is currently being paid by private individuals per square meter there?

I would have to look up the standard land value, but the directly adjacent property with 483 sqm and old building (house to be demolished) was sold for 150k. Edit: that is probably about three times the standard land value!

Then the demand is there, the benchmark is irrelevant. I would simulate both and compare, everyone has a different point from which the foreseeable effort is worthwhile.

You forgot the value of the property, which correspondingly reduces the return

I left that out because I get the impression that the OP does not want to sell. So it is "useless" capital. Of course, you can also calculate the interest on equity. But right now I don’t feel like dealing with management costs, taxes, and all that fuss...

I left that out because I have the impression that the OP does not want to sell. So it is "useless" capital. Of course, you can also calculate the return on equity. But I don't feel like dealing with operating costs, taxes, and all that stuff right now...

I just think that the land price is already relevant to correctly estimate the capital invested, in order to determine the return. The impact is significant. Without wanting to go into detail.

Then the demand is there, the benchmark is irrelevant. I would play through both scenarios and compare, everyone has a different point from which the foreseeable effort is worth it

The demand is probably already high. Today I saw an ad on Kleinanzeigen and contacted the seller. He has a plot of land about 1300 sqm for sale with a demolition property on it. I asked about the price, since the ad only said "negotiable". The answer was from €275 per sqm and by highest bid.

I don’t want to force anything. But surely everyone knows that as soon as the topic of building and land or something similar comes up, it starts with "if I were in your place…" and this has been going on for the last 6 months. Everyone would either build for themselves or a multi-family house to rent out. So the idea arose to play it through. If it doesn’t work, we certainly won’t ruin ourselves.