the first 3% are definitely the seller's commission. after all, they don’t work for free and often these sellers are commission-based employees. creating the documents for the building notification, on the other hand, is real work that not just anyone can conjure up out of thin air. at closing, there is another 2%, which together with the first two mentioned makes 10%. then there are 9 individual trades each with 10%. theoretically, the payment plan is designed so that the construction company always performs in advance and gets paid after the work is done. the 3% can be earned upon signing, for example, if these represent the costs for the seller. after all, you caused costs for the company by talking to the seller and so on... (administrative costs) in practice, however, it is so that almost all payment plans are designed so that you pay in advance. 50% is good until the completion of the enclosed shell (roof + windows are in). but there have already been plans with 70-80%. 50% is hardly ever offered, usually you end up with just under 60%. much more important than the percentage amount during the shell construction is the amount paid when the screed is installed. because then there is a long pause due to drying, a lot of time during which companies can go bankrupt. and especially what comes after that can still be planned and carried out by yourself if necessary (final installation of sanitary, tilers, connecting sockets, etc.). you just have to have enough money left for that. and 2% at the end are of course a joke. the final installment should ideally be 5% and only paid when the house has been handed over. but hardly anyone will agree to that. maybe you should have your contract checked by a professional again. especially the construction time guarantee (with reasonable final compensation payment that really covers all delay costs) as well as missing items that are being hidden from you for now (port-a-potty ^^ etc.) can be recognized at a glance by a professional and they can possibly make suggestions for changes or warn you about what you are buying.