Building a house - Is the budget for building a house okay? Who has experience?

When have you planned to pay off the house?

That would be 31 years

500 euros for food is too little.

Counterexample: Four people (children 4 and 6 years old) in 2014 with 492 euros/month for nutrition. And in my opinion, that is rather high because we all eat lunch out (canteen, daycare catering).

Regarding the initial question: 100,000 euros equity, 3,800 euros net income, 30 years old ====>>>> Of course you can build! Just ask your house bank without obligation how much loan they would give you today. Then look at house offers on common real estate portals. For new builds, you have to add another 50,000 to 100,000 euros to the internet price (and possibly the land). For existing buildings, you can first calculate with what is listed there plus land transfer tax and notary/land registry fees.

Counter-example: Four people (children 4 and 6 years old) in 2014 with 492 euros/month for food. And in my opinion, that is rather high because we all eat lunch out (canteen, daycare catering).

That doesn't get us far, and we don't eat in the canteen.
3 people 200 euros per week.
Surely it depends on personal needs, e.g. meat from the discount store or butcher, same with bread.
In summer it is certainly 50-100 euros more per month, grill time.
And at Christmas oh dear, the turkey already costs 50 euros.

So we spend about 70 euros per week on food, there are three of us. However, we do not buy meat, but otherwise almost only fresh food. Still, we by far do not come close to such a high amount over 100 euros.

We are 4 people and easily spend 80-100€ per week on food + another 50-100€ on the drugstore,... It also depends on the regions here. In some areas, groceries simply cost you more!