ᐅ Single-Family Home Construction: Planning a Granny Flat / Accessory Dwelling Unit for Future Family Expansion?

I have a general question in the hope that you either completely dismantle the idea or that it might be workable. It’s more of a rough idea than a concrete plan:

We (a couple planning to have children but currently without any) would like to build a single-family house on a relatively large plot of land (1000sqm (10,764 sq ft)). Since we plan to have two children in the future, we would like to design two children's bedrooms accordingly. A home office and possibly a guest room would also be nice to have. A friend who is an architect suggested incorporating a separate apartment within the single-family house.

So we came up with the idea to possibly plan the house with the master bedroom, bathroom, home office, and guest room on the first floor, and to place a separate apartment in the basement with two rooms, a small kitchen, and a bathroom, which could also be rented out. If there is a later need for two children's bedrooms, the separate apartment could be used as the home office and guest room, and the freed-up rooms on the first floor could be used as children’s bedrooms. In the more distant future, the separate apartment could potentially be used again as a separate living unit for teenage/adult children or as an accessible living space for aging occupants.

This way, there would be no unused rooms in the new build, no risk of the house being too small in the long term, and as a side benefit, there might be additional subsidies and, of course, rental income.

Completely crazy idea or possibly reasonable?

marvel-online schrieb:

Completely stupid idea or possibly reasonable?

Completely stupid idea. Build the house according to how it will be used. Anything else is, in my experience, pointless.

The idea of giving your children their own space is certainly appealing, but it is far from inexpensive or even free to realize. You need to be able to afford a granny flat or accessory dwelling unit. Can you? You shouldn’t assume it will be “cheaper” in any way, despite subsidies or financial support. Well, whether you want strangers living in your house or not is something only you can decide.

K1300S schrieb:

The idea of giving your children their own space is certainly appealing, but it’s far from cheap or even free to make it happen. You need to be able to afford a separate apartment. Can you? Don’t assume it will be in any way “cheaper,” even with subsidies. Well, whether you want strangers living in your house or not is up to you.

Basically, the main idea would be not to build two rooms for the children that initially remain unused, but rather to rent them out profitably in the meantime. The “own space” would just be a bonus for the future, after about 16 years, when you might switch back.

marvel-online schrieb:

profitable

Find the mistake. It doesn’t pay off. Instead, it’s pure luxury, and the investment can only be offset through “rental income.” If you don’t want to do something good for your children with it, you certainly aren’t doing yourself any favors either. Of course, if you have money to spare, you can do it. But in that case, you might as well build your children their own house. 😉

K1300S schrieb:

Find the mistake. It doesn't make financial sense. Instead, it’s pure luxury, the investment of which can be offset by "rental income." If you don’t want to do something good for your children with it, you certainly aren’t doing yourself any favors. Of course, if you have abundant money, you can do it. But then you might as well build your children their own house. 😉

I’m confused. The only "luxury" would be an additional small kitchen. The number of rooms is exactly what we actually want. Only that they don’t just remain unused until the second child arrives. 4 rooms = granny flat/apartment + guest room + study = 2x children’s rooms + guest room + study.
So where exactly is the rest of this "pure luxury"?