Financing plan -> Need for optimization?

Yes, you are right, I have to calculate that separately because, for example, [Baustrom] and [Bauwasser] are recorded as incidental purchase costs, which they actually are not.

The house would be a city villa with 160sqm. Solar/Gas with a Vallox controlled residential ventilation system and underfloor heating throughout the entire house. Lots of window area built from aerated concrete/rock wool/clinker KFW 55.

Special requests might be a central vacuum cleaner, as I said, it all depends on what one can and wants to afford. That’s why I’m here to see what else is possible on top.

Best regards

That's why I am here and asking

no one will be able to give you a valid price!

I also don’t want a valid price. It’s more about whether something was forgotten or opinions on standing with an income after x years with sum x behind me.

Whether there might possibly be options and ways I haven’t thought of until now.. a pool of ideas?

Regards

Ancillary construction costs for the plot such as notary/taxes etc. are already included in the plot price.

Outdoor facilities/garage are constructed independently and offset against the savings from the self-performed work (from the turnkey house).

Your financing needs depend on the construction costs.
These are incomplete. "Turnkey house" does not say anything either. In 95% of cases, you still have to do quite a bit yourself. To talk about savings in services when you still have to pay for the materials would be fatal.
For a well-organized and comprehensible calculation, this must be itemized. To me, this reads very incomplete, not properly informed by the building contractor, and thoughtlessly or deliberately forgotten items, so that one can afford it.
Take a look at the construction costs subforum.

Hello everyone, My wife and I want to build a town villa and have a plot of land in sight. Total monthly income: 3800€ Plot with all costs: 115,000 € Turnkey house: 285,000 € Best regards Mateo

Don’t be fooled by the house providers and their house catalogs/exhibitions! The houses you see there are not what you buy for 285K€. Tip: Get the price from the model house as it stands there. Or compare exactly what was offered to you for 285,000€ and what would still have to be upgraded to a “villa.” I think 285,000€ initially only covers the simplest standard. Calling it a villa is almost a deception that consumers like to hear. Definition of “villa” (Duden): A) larger, prestigious, detached house located in a garden or park [on the outskirts of town] B) large, stately country house

I also believe that some items have been forgotten. It is best to read through the [Bauleistungsbeschreibung]. Stadtvilla means two full floors, right?