Plausibilization of my financial planning

Hello everyone,

we want to build next year and I wanted to ask you to look at my current planning:

Costs:
Land (525m^2): €153,000
Land additional costs: €12,000
Basement: €50,000
House (single-family house, 150m^2): €260,000
Connections, driveway etc.: €20,000
Additional costs: €20,000
Buffer: €40,000
Furnishing: €15,000
Own work: -€5,000
Total: €575,000

Capital:
Equity: €155,000
Grant: €5,000
L-Bank: €100,000 (energy-efficient building, living with a child)
Bank: €315,000 (20 years; 2.2% interest; 4% repayment)
Total: €575,000

Income:
He: €5,600 net + bonuses
She: €0
Child benefit: €378

Burden
Old New
Rent: €800 Interest: €700
Savings: €1,400 Repayment: €1,350
Additional costs: €275 €300
Reserves: €0 €200
Total: €2,475 €2,550

I should be able to offset the difference through salary increases by the start of construction.

Do you find the calculation plausible? I have already cautiously checked the financing conditions with banks and it is probably not entirely unrealistic. However, it is probably a bit more expensive now. Repayment at the bank should be largely completed after the fixed interest period ends.

Thanks for your input!

Sounds plausible. I think your buffer is reasonable, income fits, and cost assumptions (from a layperson's perspective) don't sound too wrong.