So for us, the construction obligation was defined as a completed shell of a residential building. But elsewhere it could also be the move-in or occupancy readiness.
You should aim for 300k€ for the house. With a lot of your own work, you can certainly go lower, but you need the time, helpers, and tools for that.
How much equity do you have? As long as you keep the rate under 2000€ with a reasonable term, I would definitely do it.
I need to ask what is meant by construction obligation. In any case, it was increased from 3 to 5 years and it is rather rural.
Equity is not particularly much, around 50k€. We are 31 and 29 years old and do not want children. I recalculated our exact net income. We are at 5300€. Vacation pay, Christmas bonus, etc. are already included. I also roughly had the 2000€ rate in mind.
The plot without a construction obligation is very nice, but costs 170k€ due to its size. The plot with a 5-year construction obligation is a bit better and would cost 113k€. My wife could walk to work instead of driving 20 minutes. But it might also be that she changes her profession sometime, since she only earns 1700 net.
Such a standard house at Town & Country costs about 250k€ (turnkey) from what I saw quickly. If you can roughly stick to that with some own work and no special requests, it could work.