We are interested in a property...
Don't focus on servitude area for now. If the build is 1.5m (2m is safe) from your neigbour and 3m from street boundary, servitude is usually safe. Servitude in a nutshell is that average 2m buffer zone from your yard line inwards at all 4 sides. Look where your water meter, telephone and/or fibre poles, sewerage sits, that is the servitude area.
The problem I see is the flat. Because its not freestanding, a kitchen is not allowed. Not really a big problem, kitchen can be removed or you just pay the penalty fee for it.
I objectively don't think anything will have to be demolished. But obviously want ways to verify this without having to pay for a surveyor or an architect or any other kind of professional fee.
Agreed. Demolision only happens with real dangerous builds.
My advice:
Go see the municipal building inspector in person, don't call, and ask him to come check and give you
advice AFTER HOURS...FOR A FEE, to pay for his time and travel cost. Make sure it is NOT understand as a bribe.
He will check servitude, which i think is overblown here, but not impossible.
Ask him about the kitchen/s
If he see any other problems
A servitude breach is not a DEAD NO, you can build there with permission as long as its more to the back, on the sides. Sewerages area (back boundary) is a dead no. and of course street boundary.
If he finds nothing wrong and therefor approvable, also ask him about the possiblity of applying for an as-build plan. With this you draw plans for the whole house as it is now, making no mention of any unapproved build. This is usually what you do when you lost your plans. This way there are no penalty fees and an easier path to approval.
Whatever you decide to do, you will have to spend some money beforehand. Your mind seems made up to buy the house so start working. Also, it is really not that much of a hassle as some make it. You just really need to know if that build is passing your local code, and from there its just apply and pay the penalties.