Real estate as an addition - security to get a good interest rate

Is there a possibility that it could become building land someday? I would always try to keep land. Sell only if it is a matter of life and death.

Is there a possibility that it could become building land someday?
I would always try to keep land. Only sell if it's a matter of life and death.

I wouldn’t put it that way. If it is really fertile/relatively flat land, that might be true, but most properties are far from building land. Of course, if there is the option to install wind turbines there, that would be great; otherwise, I would keep the calculation relatively simple:
If the lease covers the repayment of the house, then keeping it is worthwhile; otherwise, it makes more economic sense to sell it. But since it is not your property, but your mother’s, the decision does not lie with you anyway. Maybe there are siblings as well who also have a claim to it.

Land is demonstrably becoming scarcer. And since it is not only about today but also about tomorrow and the day after, I stand by my statement.

It's also a bit of a mentality question. We Germans tend to always accumulate (material) possessions. I don't want to say here: sell at any price, but the other way around doesn't always make sense either. Basically, the OP is right that there are almost always interested lessees, but in our region the lease is at a relatively low level. The capital return is therefore very low. From my point of view, the big advantage of land is that it does not lose value (unlike the home). But as I said, it always depends on the individual circumstances. In many cases, people don't think about it that much, since many landowners are not the typical clientele who intensively inform themselves about investment strategies, etc.

We have farmland as collateral in our financing. This is also not yet in our ownership. As already mentioned, direct banks are not interested. Both regional banks (Sparkasse and Volksbank) would have liked to take it as collateral. In the end, we went through a loan broker to the Commerzbank and got top conditions due to the high collateral ratio. Deutsche Bank would have accompanied us as well. As a reference point for the value of the farmland, you can take the standard land values from the appraisal committee of your district. And of course, the banks do not use the full value of the land as collateral but apply discounts for realization risks. Have fun with your construction project

Perhaps as another approach: If a KfW loan is an option, it is considered equity replacement by some institutions. So, for example, if you build according to KfW55 or better and take out a KfW loan of over 100,000 EUR, this does not count against the lending value and can thus lead to better conditions.