If you prefer to live over 2 levels, then plan the two apartments to be rented out stacked on top of each other on one half of the house and your house over 2 levels, possibly 3 levels if the attic is added, on the other half of the house. So basically a semi-detached house with two residential units on one side and your residential unit on the other side (and you can take the nicer side).
Advantages:
- You have a separate entrance and do not have to share the stairwell with the tenants
- You have direct access to the attic and it can possibly extend over the entire house area and be used only by you.
- No one can stomp around over your head
- Clever garden layout gives you more of a feeling of having your own house than if someone is always looking down from the balcony above
- As storage space, you can provide the tenants with a garden shed (more cost-effective than a basement)
The previous remarks still apply of course (storage space, parking spaces for rented units, freezer room accessible to all, larger bathroom for a family of five).
Nevertheless, I also get really nervous about the financing. Let a problem tenant catch you and then the house of cards collapses. You have to be able to manage at least one year without rental income without having to ask for help. It takes ages to obtain a legal order and lawfully evict someone from an apartment. During that time you will incur legal fees in addition to the missed rent. Usually, you can be glad if you finally get the people out of the apartment. The outstanding rent is usually never recovered, just like the legal costs. Such people have no money and you cannot get blood from a stone. And don’t come with "choosing tenants carefully". It can always happen. My parents rented to a well-paid software developer who was in the hospital for a long time due to an accident that was not his fault, could not work (he was a freelancer), received no money, paid no rent, then skipped town... etc. Until you can even request a bailiff (and before that you are not allowed to enter the apartment)... as I said, count on a worst case of 1 year of lost rent plus additional costs. And you will be stuck with those. I would only do something like this if I know that I can handle the worst case. Of course everyone hopes it never happens, but you should be prepared. I don’t see that here.