Architect - Fee - Own contribution

My father built a house for my sister 3-4 years ago, since he is a professional. They stayed under 400,000.

Today you not only have the problem that costs have increased (see Zaba12), but also that you still have problems getting craftsmen at all.
And if you build in a year, you will have further cost increases by then (wages + materials like steel, for example). So it's better to calculate carefully and cautiously. Just for your information: in a normal developer house, there is a 15% profit margin for the developer. If the architect is calculating with 550 now and your budget is only 350, it will not be possible to stay within the budget even with a lot of own work.