>> 2. How does overfilling properties lead to rising prices? If anything, it would serve to keep prices lower.
When one family rents a 2 bedroom flat, they may be able to afford say 1K (husband and wife working). But when the same flat is rented to 4 singles, they might be able to afford 2000. Each person's share is just 500. So when the landlord asks them 1200, they would happily pay for it as the effective rent per person is only 300.