One obvious way to save on rent is fit more people in a room and has been used by hostels for a long time. But this has a lot of problems.

Where to have sex. When you share a room people do not like to have sex in it. Potential solution is to have a shared bedroom that can be rented as needed efficiently using a shared calendar. Since most people only have sex infrequently, its not much of a compromise.

Noise. Its hard to sleep when there are people coughing or rustling in your room. There are several options for this. Earplugs. To prevent peoples phones from going off you all need to use vibrating alarm clocks (this is what deaf people use to wake up because they cannot hear alarms), white noise such as a fan or white noise machine. A densely populated room will get hot so a fan might have the dual benefit of cooling the room and making white noise. Creaks. have a thick carpeted floor so footsteps are softened. Use foam mattress so they dont make any creaking noises. Do not use regular bunk beds since the connected frame causes vibrations to spread to both people which is annoying, so actually use a loft bed and put a mattress on the ground underneath it but not connected.

Privacy. You could buy a privacy pop to surround your bed in a tent.

illness. Closed quarter are more likely to spread viruses. You could all supplement with things that decrease your susceptibility in the first place like garlic, nac, and glutathione. Also air out the room during the day.

smell. Use an automated air freshener

Claustrophobia: since people will have low ceilings in bunks, the key is to use queen beds. It feels rather luxurious. Also mirror along the walls give the feeling of space. This might reflect sound so theres a tradeoff between deadening sound and feeling spacious. Also, put the mattress on the ground to increase vertical space for bottom bunks.

Ideally you could fit 6 people into a 2 bed 2 bath. Things that require a sink but not a toilet or shower should be done in the kitchen i.e. brushing teeth.

podshare.co understands this, but they operate in commercial spaces which isn’t legal.