I basically see it the same way as Lexmaul. But besides the time your helpers need, you should also consider the following points: 1. Do not underestimate the work that not only your helpers but also you will have to do on the construction site. Do you have the time, strength, and willingness for that? 2. If you have 2 years for the house, that's all well and good, but keep in mind that during that time you will also have to pay your loan (in addition to the rent) and commitment interest.
Regarding point 1, I can only clearly say YES, I am aware of that and fully understand it 100%. It is completely understandable that the more you want to do yourself, the harder the time becomes, and that it will be a tough time because of that. Also, considering time with your wife and possibly first child. After all, every hour and minute you invest yourself is also a euro you might have saved. Of course, under the condition that it is done correctly. Regarding point 2, from what I have read so far, there are usually no commitment interests on the bank loan in the first 12-14 months, depending on the loan. As mentioned, it probably varies from bank to bank and there are also fixed times from KFW, Labo I do not really know, during which the whole amount must be drawn. But still, no one is forcing me to be finished and move in within 6 months. I see that as a big advantage.
In my current calculation, I only listed food and everything else separately. So 1000€ and maybe a bit more can definitely be correct here. As so often, it is probably a matter of perspective.
For us, if anything, the latter would be an option, although the basement would be implemented or omitted depending on financial feasibility.