How much house can we afford?

Hello, first of all thanks for the answer. So my wife is 30 years old and I am 33 years old, we have a child who is 1 1/2 years old, further children are not planned for now. We would carry out the labor ourselves together with my father and my father-in-law and also other relatives as we have several craftsmen in the family and among friends. We do not have any other loans running and since we still live in the granny flat at my parents' (almost no rent) it is also possible to put aside at least €800 every month. We had possibly thought about contracting all the trades individually, what do you think about that?