New Single-Family House Construction - Feasibility Assessment

2.1% over 15 years? Where? With whom? Did I miss something essential? Does 2/3 loan-to-value make that much of a difference?

I assume the financing is already a few months old. At the beginning of April, such rates were last available.

A side issue that catches my eye here is the secondary employment. In the case of new construction, the extra money is of course nice, but depending on the workload, you lack the time to actively supervise the construction, and there are also things like working time laws ;-)

I assume the financing is already a few months old. Such rates were last available at the beginning of April.

Exactly, the financing has been in place since around April.

A side issue catches my eye here, namely the secondary employment. For a new build, the extra money is of course nice, but depending on the workload, you might not have time to actively supervise the construction, and there are things like labor laws ;-)

Yes, absolutely right, one might have to reduce the time invested in the side job a bit. Overall, however, this should hopefully not jeopardize the implementation.

That all looks very good, but it will fundamentally change once the planned 2 children arrive. Then there will be no more 900 EUR living expenses per month and both working full-time plus a side job.

Also keep in mind that expectations will increase at some point. In your mid-20s you are still content, that changes later... and with children anyway.

Also with the studies. I don't want to offend anyone, but with us (Electrical Engineering) only 40% made it. Counting on graduating before you’ve even taken the first exam... that’s ambitious...

Calculate the "bad case" (not the worst case) again and consider whether you can handle that. The bad case will look like you’ll have to do without many things for many years, and the children too. If that works for you, then you can get started.

Is there still something to save on with the house? Does it have to have a basement? Does it have to have a garage?

That all looks very good, but it will fundamentally change when the planned 2 children arrive.
Then there’s no more 900 EUR living expenses per month, and both working full-time plus a side job.

Also keep in mind that demands will increase over time. In your mid-20s you’re still content with little, that changes later... and especially with children.

Also with the studies. I don’t want to offend anyone, but with us (Electrical Engineering) only 40% made it.
Counting on graduation before even taking the first exam... that’s quite ambitious...

Calculate the "bad case" (not the worst case) again and consider whether you trust yourself to manage it. The bad case will look like this: you will have to give up a lot for many years, including for the children. If that works for you, then you can get started.

Can some savings still be found on the house? Does it need to have a basement? Does it need to have a garage?

Thank you very much for the comment, especially for the critical questioning.

Regarding his income: His income will probably increase in the next few years from currently just under 80k to probably 90-100k. Whether he can keep the side job when there are two children remains to be seen.

Regarding her degree: If the studies do not work out, which I don’t believe, she could probably return to her previous job; the current job market situation looks quite good, meaning €2000 net per month in the bad or worst case. In the good case, with two children in 5 years (A9, level 2, 2 children) she would likely earn about €2450 after deducting private health insurance (excluding inflation-driven "collective wage increases").
Part-time (50%) that would be €1400.

That means the bad case would probably be his income without side job (and without any increases in the next 5 years) and her halved income (50% part-time) in her previous job, €3800 + €1200 = €5000. Also, for the bad case we assume that they don’t get married or that the tax advantage from joint filing is abolished.
Do you think that in 5 years this bad case with an income of €5000 per month could endanger the plan?

Plus: the portfolio of €110,000 would still be available, which could be drawn on in the worst case.

In the good case, she would be there in 5 years with two children (A9, level 2, 2 children)

How does that work? How long is the degree program (I have 3 years in mind?)? That doesn't count towards the level duration, right, and parental leave doesn't count either?! Should child 1 be born during the degree program?