just take a look at how it looks or costs:
- if I do the real estate financing without Wohnriester (without the 23,000€) I pay interest X for J years = interest paid
- if I bring the 23,000€ as additional equity, then I pay interest Y for J years = interest paid for that
and then you see how high the savings are.
in point 2 you look at when you retire, example in 30 years = then you capitalize the 23,000€ at 2% for the years = amount R
from amount R you subtract the 23,000€ = Wohnförderkonto, which must be taxed
(and then you can just estimate, for example assuming you then have to tax 18,600€, you do it in one go, with 30% discount, so 13,000€ is taxed, with 35% as an estimate = that is 4,550€)
the assumption is that further Riester savings/contributions have nothing to do with it, only that you withdraw the 23,000€ once.
so the option without Wohnriester costs 5,000€ more, then I wouldn’t bother, especially if you don’t know exactly how it will look tax-wise in the future.
if you save maybe 10,000€ in interest, it might already be interesting.