I would work backwards from the lowest plausible valuation supported by the completed comparables, not from the competing bids. Then ask the lender how that figure changes the cash required. If CHF 44,000 still leaves room for inspection findings, keep the cap and state it plainly. If not, lower...
Local supply should be narrowed beyond Zurich as a whole. Buyers and tenants compare immediate alternatives: location, transport, outdoor space, noise, parking and floor plan. Those factors may dominate the villa/duplex distinction when you eventually sell or let it.
I would challenge the assumption that the villa is simpler to maintain. It may be simpler administratively because there is nobody else involved, but every exterior component is then yours alone. Simplicity of decision-making is not the same as a lower maintenance burden.
Permit timing should be tested against that list of energy measures and any building alterations. Rather than assume the whole project needs the same process, ask the relevant Zurich authority or project adviser which specific items require approval and how that affects the intended start.
The main constraint is that the margin looks modest once all recurring ownership costs are included. I’m considering a 3-bed detached home in Zurich for CHF 668,800, with projected rent of CHF 3,088 a month. On the purchase price alone that is about 5.5% gross.
I have allowed for empty periods...