Is the financing plan realistic?

Which federal state are you from? In Bavaria, for example, the Bayernlabo could help you further. From 15% equity and corresponding maximum annual income limits, there is 1/3 of the total costs as a full repayment loan over 30 years at 1.75% - the money is considered equity capital by other banks because the Labo takes second rank. Other federal states, to my knowledge, have similar funding models.

Best regards

Yes, we are from Bavaria. I need to take a look at it, thank you very much.

I would need to check again during the sampling.

But the 272,000 includes the foundation slab. Flooring is also included as well as painting work (plastering & painting).

Well, you are asking if your construction financing is possible like that, you have now heard twice that your house costs are set too low. Nothing more is within my power : )

All the connection costs are included in the ancillary costs for the property.

I think this leads to confusion. Are all the earthworks included as well?

Normally, one itemizes as follows:

[*]Land + incidental purchase costs
[*]House price
[*](depending on the level of completion, additional items)
[*]Ancillary construction costs (including earthworks, connections, etc....)
[*]Garage
[*]Buffer, buffer, buffer

Then it might fit better with the comments of some here.

Roughly from my point of view, buffers for earthworks (where you can sometimes spend 15-20K more), as well as a buffer for selection (10-20K to be on the safe side) are not considered in the calculation.

How high are the ancillary construction costs assumed? 40K? Or less?

Find out what the price per square meter is for the floors that will be charged to you. Depending on the choice of covering, a few thousand can quickly add up. The same goes for the tiles for the bathroom. The lump sum for sampling has already been mentioned. I believe hardly anyone likes the standard. The electrical package needs to be scrutinized. It is often set too low. Do you already have a soil report for the plot? That would be important to estimate the necessary earthworks. How expensive are your connection costs? Sometimes there are nasty surprises (for us, a sewage pump costing almost €8,000 that we hadn't planned for).