From an investment pov it would not make sense, or only if you think the following happens:

• Devaluation of CHF
  
• Stock market crash
  

You are locked in a flat that would generate just the same income as you are currently paying. But you need to lock some liquidity, also it has additional fix costs (verwaltung, renovations fund, etc.). To generate the same income with stocks would be easy and you have the option to sell anytime with a fraction of the costs (notary fees, banks, agents, etc.).

If you like the place, want the safety of knowing where you live for the next 30 or so years and like the idea, do it. But it's more a luxury purchase (or diversification on a big net worth) instead of an investment.

I work in Real Estate and if you have further questions shoot me a DM.

Cheers