Should be roughly neutral in effect; the money is pulled out of the rental side of the housing market by people who aren't able to afford sole purchase going together to do a joint purchase and going into the owner-occupied housing side that way, but that either drops rental prices (making purchase at high prices less attractive) or gets current rental units sold off into the owner-occupied market because they are unable to make enough to be profitable as rentals, increasing supply on the owner-occupied side and dropping prices.
So not viable after all then. The only solution I see is build higher and denser, and do it so much that it can accommodate the demand growth.
Unfortunately between existing owners working to kill any new units and renters in SF claiming that building more increases rent (and vying for rent control which makes things worse) I think it’s just hopeless.
Your suggestion seems to be to just buy the place and have your friends be roommate tenants? The reason this isn’t viable is the costs are too high.
By buying a place together you can get a better place with an affordable mortgage split and you can share in the upside without getting locked out of the market.
The risk is the standard social risk plus the risk that if everyone does this prices will get even crazier.