This tool from NY times seems to be flexible enough to be used for Switzerland as well:
In particular it accounts for the opportunity costs.
I do not do currency conversion and just use $ as CHF for simplicity, here are my fixed long-term params, what do you think?
mortgage rate: 1.2% (adjusted by discounting the marginal tax rate)
home price growth rate: 2%
investment return rate: 4%
inflation rate: 1%
property tax rate: 0.5%
marginal tax rate: 35%
cost of buying home: 3.5%
cost of selling: 5%
renter insurance: 0.5%