Is the payment plan okay like this?

Hello, I wanted to ask what you think about the following payment plan: 5% of the flat rate price after handing over the complete building application documents to the client. 5% of the flat rate price after completion of the foundation slab. 60% of the flat rate price after the start of the construction of the prefabricated house, at this time the building structure is erected, windows, roller shutters, front door installed, roof covered, as well as sanitary and electrical preparation carried out. 20% of the flat rate price after rough-in installation, at this time all ceilings and walls are covered with plasterboard, sanitary and electrical installations carried out without final assembly, the heating installed and the screed applied. 10% of the flat rate price after complete finishing, house handover and presentation of the final invoice. What do you think about it? I would be happy to hear your opinions....