Good ideas and you don't need to even work in a startup to appreciate or implement them. I manage properties in SF and one of the most common thing I do is rent out rooms in multi-unit properties and converted houses in the $500-$600 range and everyone works together to make the common areas enjoyable. IMO the catch is, at what tipping point are you willing to stop sacrifice privacy for savings? Single Mustachians might accept this living arrangement and enjoy it, but for many working professionals in SF, they are willing to pay more for privacy and conveniences. YMMV.