Financing single-family house with granny flat for parents

It's all a bit vague, unfortunately. Your wife's salary is excluded, okay. But how much does she earn if you include it again? Part-time? Full-time? How much does the daycare place cost in Hamburg? For me, in Hannover in 2018, it was almost 400 EUR/month for full-day care...

Household budget okay. 500 EUR are saved, that's 6,000 EUR/year. How do you want to build up even close to 450,000 EUR equity from that? Are expenses for furniture, vacations, new bicycles, clothes, etc. included?

PS: And have you really calculated all the costs that come up with the house? It's not just the installment to the bank. For 220m² you will have considerable additional costs... and such a plot also needs maintenance, those are ongoing costs.

I find the discussion about a "dream" house on a non-existent plot of land with a significant financing gap in one of Germany’s most sought-after major cities quite pointless. If you manage to find even a hint of a plot of land that fits your plans, you can ask the question again.

Oh, I completely overlooked that. 650 EUR/m² in Hamburg? In Hannover (city area) you won't get a plot for less than 900-1,000 EUR/m².

I don't know the construction prices in Hamburg exactly, but in the south you can't get by with €3000/m2 anymore for quite some time.

Standard land values in the south of Hamburg are around €650/m2
- Planned plot cost: €550,000

I understand it as meaning not the south _of_ Hamburg, but south of Hamburg. If I’m misunderstanding, please correct me.

I assumed that since you , in the 2020 thread with the two dream plots (which apparently didn’t work out, even though everything was from the family), you said that despite a good income you can’t afford a house _in_ Hamburg.

Just as things with your dream plots fell through, although it sounded more or less safe with the plots, it will probably be the same with your thoughts _without_ a plot – a lot of theory that doesn’t help much.

Although the south of Hamburg, i.e. Lower Saxony, has always been somewhat cheaper than elsewhere, plots don’t grow here like mushrooms in the forest either.
If you search Immonet for plots, you do find "affordable" ones, but they have a low floor area ratio, so with 1000 sqm and a floor area ratio of 0.13, only 130 sqm may be built on.
With your €550,000 – I think – you won’t have many options in Hamburg. The shape of the plot also has to fit if you want two entrances on two sides. Four parking spaces must also be planned and considered.

- A single-family house (approx. 150 sqm) with a granny flat (approx. 70 sqm) is to be built, a total of approx. 220 sqm

The granny flat is on the ground floor, similar to this floor plan which we basically like

The FamilyStyle 26.01, for example, already has 265 sqm stated. The footprint is just under 165 sqm.
So I think with a 70 sqm granny flat you won’t manage 220 sqm with 3 children’s rooms in 150 sqm.
Also, the 26.01 has no storage space, as it is designed with a basement. So you would have to generate additional space. Especially for children, you need quite a lot of dry storage space (sports equipment, shoes, and a vehicle fleet)...

Planned house costs (at €3000/sqm; is that realistic?): €660,000

No, I wouldn’t calculate like that, because due to the granny flat you are using more expensive sqm, for example bathroom or barrier-free features, which also consume valuable and costly living space sqm.

- Are there experiences/tips whether the utility room is needed only for the single-family house and the granny flat is "served" from above (without its own access for the granny flat)

You can only plan with one technical room; that’s no problem for the granny flat. That’s what a granny flat is for. However, a full apartment also needs a washbasin, drying facilities, and storage space for vacuum cleaners and so on.

- Do you have any other topics/tips you would like to give us?

Read through this thread: pretty current, exactly your topic, and with lots of tips from us...

https://www.hausbau-forum.de/threads/grundriss-haus-mit-elw-verbesserungsvorschlaege.44068/

The parents are still comparatively young and fit, and I hope for a 20-30 year rental relationship

...because I also see the problem in your case that you can’t put parents who themselves have owned a house into a small 2-room apartment. In our building area, there are plenty of seniors/retirees who built 100 sqm plus. Or who bought a penthouse apartment with 120 sqm. I don’t believe they complain about having too much space.
You can manage with 70 sqm if it’s a seasonal apartment in Spain or the apartment is only used sporadically (travel, motorhome).

I’m a bit surprised about some of your questions, because your wife is an architect, right?! She should have a real treasure trove of knowledge?!

The FamilyStyle 26.01, for example, already has 265 sqm, at least stated. The floor area is just under 165 sqm. So I think that with 220 sqm and a 70 sqm granny flat, you won't manage 3 children's rooms in 150 sqm. The 26.01 also has no storage areas, as it is designed with a basement. So you would have to generate additional space. Especially for children, you need quite a lot of dry storage space (sports equipment, shoes, and vehicle fleet)...

I can only shake my head if 150 sqm without a basement is not supposed to be enough for a family of four. I don't see 3 children? Is another child planned?

I can only shake my head when 150m² without a basement is said to be insufficient for a family of four.
I don't see 3 children? Is another child planned?

The 26.01 _does_ have three children's rooms and is very generously designed. The upper floor has 127 sqm of space! So more living space than the 150 sqm the OP considered for the main apartment. I'm not even talking about 4 people here!
So I would first add 1 and 1 together before shaking my head dismissively!

And yes: the OP expressed his wishes for 2-4 children in 2020. That may have changed without a doubt, but that doesn’t change the fact that the 26.01 (or let it be another house) simply has to be quite large in floor area if both units are to fit on the ground floor.