Opinions on the floor plan of a semi-detached house as a boundary development

Hello everyone
My brother and I each want to build our own house with a rental option in the basement on my grandparents' property. We are currently both single, but it should be planned in such a way that a future partner can also have space in the apartment, hence the apartment size.
We are currently working on the revised draft from the architect with a very detailed cost estimate that includes everything from the demolition to the lawn seeding and the garage.
This amounts to 850,000 for both houses. We are currently seeing if we can reduce it so that the limit of 800,000, i.e. 400,000 per house, can be maintained. Since I am skeptical about meeting the costs, it is also under consideration to build the design turnkey with a company using solid construction instead of working with an architect.

We would be very happy to receive an assessment of the design, as well as suggestions for improvements and points of criticism.

Thank you in advance!

Development plan/restrictions
Plot size approx. 600 sqm
Slope no
Site coverage ratio
Floor area ratio
Boundary development
Number of parking spaces: 2
Number of floors
Roof shape gable roof
Other requirements boundary development

Requirements of the builders
Rental option in the basement, apartment max. 120 sqm
Number of persons, age per house 1 person each, 37+39
but a possible future partner should be considered
Room requirements on ground floor and upper floor 100 sqm distributed over ground and upper floor
Office: family use or home office?
Guests per year 5-10
Open or closed architecture mixed
Conservative or modern construction method classic
Open kitchen, kitchen island closed kitchen
Number of dining places
Fireplace no
Music/stereo wall no
Balcony, roof terrace balcony yes
Garage, carport
Utility garden, greenhouse
Further wishes/special features/daily routine, gladly also reasons why this or that should not be

House design
Who designed it: architect
What do you particularly like? Why?
What do you not like? Why? front house terrace not private, visible from the street
Price estimate according to architect/planner: both houses 850,000 incl. demolition of existing house
Personal price limit for the house, incl. equipment. 750,000 plus furniture and kitchen
Preferred heating technology: air heat pump

If you have to do without, on which details/extensions
- can you do without: living area sqm can also be smaller
- cannot do without: basement finished as "hobby room" for rental income

Why is the design as it is now? based on neighboring development
Which wishes were implemented by the architect? shared technical basement, 2 separate houses each
What do you think makes it particularly good or bad?

... just now seeing the thread ... unfortunately, little can be seen because it is simply too small.

What kind of building is that in the north? And why rent out the entire basement development as mini-apartments with only one light well? Who is supposed to rent that? Especially since the entrance is probably next to the private terrace.

In general, I find the approach with the kind of courtyard interesting.