Bungalow with basement for single-family house with 60m2 office, is it reasonable?

Dear Construction Forum

I am still at the very beginning of planning a single-family house. The following framework conditions apply:

[*]Plot available, all roofs and building types allowed
[*]House construction budget: 500,000 EUR including ancillary costs and kitchen
[*]Living area 115m2
[*]Office with 60m2 (single room)
[*]Double garage
[*]If possible, KFW 55

Currently, I am trying to find out whether a bungalow could work for the desired project. The idea would be as follows:

[*]Since the plot is relatively large (712m2), a bungalow could be placed
[*]The bungalow would have a relatively small but sufficient living area
[*]The bungalow will be fully basemented and, except for the "office," the basement will be usable storage space
[*]The office will be the only basement room equipped with heating.

Very rough cost estimate (so far without soil survey):

[*]Bungalow: 115*2500 => 287,000 EUR
[*]Basement: 115*750 => 86,250
[*]Ancillary costs: => 74,650 (20%)

I see the following advantages to the idea:

[*]Everything necessary for daily life on one level. Especially when getting older.
[*]Office cooler in summer than on the upper floor
[*]No sloping ceilings in the office
[*]Technical room can be placed in the basement
[*]Additional usable/storage space in the basement

Does the proposal make sense, or would a two-story single-family house with about 150m2 be more sensible, especially for the plot? The office would then be on the upper floor but would have to be smaller. The main advantage of this solution would be the additional garden area.

I am aware that all this is still very rough. My goal in the first step would be to find out what possible variants there are.

Many thanks for all tips and advice.

Office with 60m2 (single room)

Even as an open-plan office, the size does not sound like managing own assets, but rather like an official business premises with an emergency exit and further occupational safety etcetera, milk and sugar.

The 60m2 should not only be used as an "office" but also as a workshop. 60m2 would also be an ideal size.

The 60m2 should not only be used as an "office" but also as a workshop. 60m2

I thought you would then work from home in the "dark" basement as an office. 60 sqm? Now you come around the corner with a workshop. Who needs 1 room with 60 sqm in the basement for what purpose?

[*]Bungalow: 115*2500 => 287,000 EUR [*]Cellar: 115*750 => 86,250 [*]Additional costs: => 74,650 (20%)

The costs of the cellar seem significantly too low to me. 33% of the above-ground construction costs can't be right, can it? Otherwise, everyone would build with a cellar. In general, above-ground living space, practically your office, is usually cheaper.

The description was unfortunately not quite ideal. A "office" with 60m2 would actually be a bit exaggerated :)

The idea was to do without an office in the regular living space and to set up an "office corner" in the workshop. That would be sufficient in my case. Primarily, it involves electronics work at the workbench with a soldering iron. Basically, I see two possible variants for this:

Variant 1 (large workshop)

[*]Bungalow with living space 115m2, without office
[*]Basement with workshop/office combo.

Variant 2 (small workshop)

[*]Two-story single-family house with 150m2
[*]Workshop on the upper floor, 30m2
[*]No basement

Regarding the costs, I only made a very rough estimate based on common information from the internet. For basements, 500 EUR per m2 was often mentioned. Therefore, 750 EUR per m2 due to the additional heating and insulation. However, this was probably too optimistic.

Overall, the following questions arise for me:

[*]Is variant 1 really much more expensive than variant 2?
[*]Is there possibly a variant 3 that should be considered?
[*]Must one also calculate 2500 EUR per m2 for a heated/insulated basement room?

Many thanks.