House Construction Financing (Patchwork Family)

Hello forum community,

for our planned major project, I ask for honest assessments, comments, and suggestions:

Goal:
Purchase of land and house construction (single-family house) in a small community in BW.
A new development area is currently being developed; building plots will be available for sale in late summer.

Marital status:
We are both 36 years old and not married (wedding planned in the future). My partner has 2 children (9, 10) who live with us. My daughter (6) is a weekend child.
Currently renting a house for 1,100 euros rent plus 300 euros additional costs. The house is fully furnished and like new; only a new kitchen is required.

Income: M: 2,800 euros net (tax class 1) including company car, minus 330 euros maintenance. 12 salaries plus bonus (approx. 4,000-5,000 euros net p.a.)
Income W: 1,550 euros net (part-time public service) plus 580 euros maintenance plus 368 euros child benefit. 12 salaries plus 50% Christmas bonus.
Total: 4,970 euros net per month
Monthly savings rate: at least 800 euros

Costs:
- Land 425 m²: 96,600 euros
- Notary/property tax: 6,400 euros
- Prefabricated house with heat pump 160 m² (without basement) 260,000 euros (own work for painting/wallpapering and floor coverings except tiles). First offer is available.
- Material costs interior finishing: 10,000 euros (simple standard)
- Single garage: 6,000 euros
- Material costs outdoor facilities (own work): 8,000 euros
- Kitchen: approx. 6,000 euros (simple standard)
- Additional construction costs: 40,000 euros (estimated), without gas connection
- Buffer: 10,000 euros

Total costs: approx. 445,000 euros

Equity:
Savings account, stock funds: 40,000 euros
Riester (together): 18,500 euros
Building savings contract: 13,500 euros
Total: 72,000 euros

Financing requirement: approx. 375,000 euros.
Repayment: 2%
We dare to afford a rate up to 1,500 euros/month.
Financing via KFW bank plus annuity loan and possibly residential Riester.

Many thanks in advance for your support!
If I have forgotten anything, please feel free to ask.

Hello everyone, does no one have a comment, criticism, or suggestions? In your opinion, is the project feasible?

For a loan of 375,000 euros, I would rather expect a payment of around 2000€. The rule of thumb is about 500€ per 100,000. It is important that you should repay at least 2 percent. For this amount, I would also consider a fixed interest period of 15 to 20 years at least. With [Kfw], it is always 10 years. You should not forget that. Otherwise, just get a few offers from the financial service provider and see what they say about affordability.

I would only partially include the child support for the kids living with you. In about 8 to 10 years, this will cease or at least decrease. By then, the first [KfW loan] will not even be repaid yet.

Have you ever calculated how long you will be paying off the loan with a rate of €1,500 p.m.?

. 1. Training (or studies) are subject to maintenance obligations. Therefore, the period is somewhat longer. Also, with this justification, the maintenance I have to pay would also cease. But you are right, a buffer is important, especially since children have higher demands as they grow older.

: 31.7 years (according to Interhyp with an interest rate fix of 15 years, 2% repayment, 27% effective interest). Without consideration of Kfw and/or family support L-Bank (BaWü). We have an appointment for this today). Special repayments not included, interest rate naturally constant (which we all will not assume).