Regarding ownership - I wouldn't assume 1.5% mortgage interest rate forever. Maybe 3%.
Then the Eigenmietwert which increases your taxable income and the maintenance costs.

Care to provide us with a source for that information? I believe that you are misguided, but I am quite happy to apologise if you can prove me wrong!

Here you go with the source. You probably need to use google translator

http://www.admin.ch/ch/f/rs/220/a272.html
http://magazine.immostreet.ch/fr/200...-proprietaire/

It happened to me that there was an apartment i intended to buy in Lausanne. The tenant managed to extend his lease by one year.

Thanks for your sources Ella, but nowhere does it say that the tenant has a "right" to extend by two years. It says that the new owner can give notice to the next legal/contractual notice date but that the tenant may appeal. An appeal may not necessarily be accepted and the tenant has to prove that having to move out will cause considerable problems. The tenant must also demonstrate that he/she has tried everything to minimise the problems. This is more likely to be the case for a family with children that may have to change schools than for a couple with dual income and no children. Of course an appeal may also be lodged if the tenant feels that the reasons given by the new owner are not "valid" reasons for giving notice (ie getting one tenant out so that the landlord can increase the rent for subsequent tenants). And in fact, the maximum period that an appeal can be granted for is 4 years for housing.

I also know of cases where tenants have managed to remain for longer in a building that has been sold, but it is not a given.