Is buying a house as a temporary solution reasonable?

A lot has already been written. The following would stop me from doing it:

- Acquisition incidental costs are lost in any case. (you will be able to pay a few months’ rent with that.)

- Currently, properties are being sold at peak prices, which will almost certainly lead to a loss in value.
An exception might be the so-called BOOMTowns. Prices there might even continue to rise.
But with €350,000 you won’t get far.

- In maybe 5-7 years, many of the first 10-year loans will expire. Since many only amortize at 1% for 10 years, an interest rate increase of 2-3% could flood the market with quite young properties.
([Immobilien Blase platz], many foreclosures)

- A house has significantly higher incidental costs than your rented apartment, provided it is reasonably up to date.

- As a homeowner, you bear the risk of a broken heating system, a burst pipe, or whatever else.

- Probably the commute will increase if you currently live in the city and thereafter maybe rather on the outskirts.

- Lastly, of course, the high interest burden. That is lost. If you currently have a lot of equity,
that might even still bring interest income, as little as it may be :D

- Moving, possibly new furniture/kitchen might also need to be considered.

You see, many things speak against a house as an interim solution. But maybe an existing property might actually be an option.
With €350,000 you will almost certainly have to build without a basement. Maybe a property around €250,000
+ €100,000 modernization is worthwhile.
With us, this option didn’t exist, since the market is empty and you even pay more for demolition houses than our house cost.
Due to the high land prices.

The best solution would be IF it can be sold with little loss in value. You yourself have already said that the risk is (too high) depreciation. And in my very personal opinion, that will occur in the planned period (a few years ...) due to falling real estate prices. Even in current "boomtowns" like Munich.

So, I can't imagine that prices will fall so drastically in Munich over the next 10 years, and there are also other cities where one can even assume that prices will rise (and which are still relatively cheap now), but moving to such an area is probably out of the question because Schnie doesn’t want to move all across Germany with the family and the job. The biggest problem, however, are the high costs incurred when buying a house (notary, land registry, broker fees, etc.). Roughly speaking, you should already calculate 7-10% for this, and for that you can live several months in a rented apartment. In addition, it is much easier to move out of a rental apartment than to sell a house again. Furthermore, you cannot sell the small house first and then build the new one; where would you live in the meantime? And that will definitely not work with the described financing. So I would definitely advise against an "interim solution house." Rather, you might want to consider not building yourself, but instead buying an existing house if nothing happens with the plot in the foreseeable future. Best regards