How will the parents give thir daugther the 300k? As a gift or as a loan?
If as a loan I do not think it will count toward the needed 20% self financing. Means the girl as to bring in 200k on her own, wheras as a maximum of 10% of the purchase value can come from pillar 2.
So we are either at a 500k or a 700k mortgage.
Unfortunatly, until now the Tragbarkeit is calculated based on a 5% interest (25k or 35k), on 1% maintenance cost (10k), and amortisation down to 66% (0 or 2.7k)
This should not be more than 1/3 of the income.
Means she must either earn 105k or 144k.
It may be that if the parents act as a fully liable guarantor (Surety/Bürgschaft) that the income can be lower.
If she gets the loan it is very advisable to safe the difference between the actual mortgage interest and the hypotheical 5% and not use it for an easy, simple, happy life. Because, after 15 years when the mortgage is up you may need this money to knock down the loan. In 15 years it should be possible to save up 400k.
With this you can lower the mortgage either to 100k or 400k and still aford to the loan even if interest rose to a now ubelievable 7%.
Raifaisen want's to intruduce a new caluclation which is suspect to apporval by FINMA. http://www.nzz.ch/wirtschaft/neue-si...raus-ld.128918
In this caculation a 3% interest is used for a ten year mortgage and the amortization of loan is much higher. Exactly that you have a much lower total dept in ten years and you could afford an interest hike.