Semi-detached house - what should you pay attention to?

Pay attention to what you would also pay attention to in a single-family house: damp basement, mold or moisture corners, building fabric, facade, windows, heating, etc...

When you drive towards the address, pay attention to your feeling as you drive through the nearby street sections. What feeling does the house give you?
If it is classically overgrown and dark, you can remove vegetation to bring in light. Usually your gut already tells you in the hallway whether you are positively curious about the other rooms or would rather turn around. But beware: if you don’t have a fundamental sense of space, you can also be blind to the potential of the house.
Furthermore, the layout must be right.
Is it again a very old property? With a 10-year-old house I would probably look differently than with a house from the 70s. For example, asbestos is then also an issue.
Do you have the number of the exposé?

That does not have to be due to the wall thickness - there can be a single-shell partition wall, and stair fixings can also transmit vibrations to it that have nothing to do with walking on the stairs.

Yes, that may be. However, since the phone calls can also be heard, I would still at least question the thickness of the wall. Of course, it can be completely different with the object in question here.

... and on the topic of "wall to wall":
One should pay attention to whether barbed wire has already been strung between the properties. Also, I would watch whether the neighbors have their garden under control or if the entire wild growth is spilling over.
Personally, I probably wouldn't mind a neighbor who is content with _one_ children's play item in the garden and prefers to sometimes visit the public playground with the children, rather than the neighbor turning out to be a day-care provider and having 5-6 children dancing around their giant trampoline eight hours a day.
I would also be cautious with an English lawn or a tractor tinkerer, although you can usually avoid the picky residents.

Even though they are two separate houses, at least the roof is often continuous, at least ours is. It was also a building requirement to design the facade uniformly, including the window color and, of course, the roof tiles. So simply red instead of black is not possible, nor painting the brickwork in color or such jokes. Honestly, I don't know what would happen in 15 years if we were to sell, and the successor then, for example, installed new windows (currently gray) in white. Whether anyone would even care then.

When it comes to sound transmission, it really depends on the construction method. In our case, you don't hear everyday noises from each other; in the semi-detached house where I woke up, which must be from the 80s, you only heard something occasionally if you were on the stairs and it was noisy over there.

On the terrace, of course, you hear each other; that can’t be avoided directly next to each other.

True, I would also be interested in the neighbor’s garden.

The house is no longer online, so unfortunately I cannot provide a link. We have already driven past it and it looks very well maintained, including the garden of both parties. What might also be quite good is that you can see that the main rooms are not located on the shared wall but on the outer wall (living room and bedroom, for example). I am very curious to see what it looks like inside. The two halves are already painted differently on the outside.

I would just be interested to know if there is anything special to watch out for, since another party also lives in the same house. What are questions that one should specifically ask for that?

Living in a semi-detached house is basically like living in a single-family house, only the neighbor is closer. Therefore, as always: Don’t just choose the property, but also the neighbors.

Am I then more restricted in my "house design"?

Yes, of course you are somewhat more restricted in house design in practice when it comes to the outdoor area, because it makes sense to coordinate. Of course, you can simply enforce your rights, but that is pragmatic in very rare cases. We currently live in a terraced house and can hear the neighbor’s boy on the right practicing piano, on the left just the occasional chair scraping on the tiled floor. The neighbors can of course also hear us when we play music, our youngest wants to become a bassist and the low tones come through well. We know this about each other and are considerate, for example in the evening hours.