...or just build enough housing, that whoever wants to buy it, can buy it at some normal percentage above construction costs, and enough rental properties exist, that landlords have to lower the prices of rent to get someone to live there.
If you're stuck at a "pay way too much for rent" or "commute for 3 hours every day" choice, and if you don't take the too expensive apartment, there are 10 other people interested in it, it's a pretty shitty situation to be in... and here in Ljubljana Slovenia this is happening just now (college starting soon, students looking for apartments).
Leaving apartments empty is not worth it, since you still have to pay for monthly costs (power, water, heating, even if empty), and the only way to be worth it is, if the price of the apartment rises higher than the monthly costs.. and that is only true if (almost) no new apartments are being built. If we built enough new apartments the prices of used one would go down, making apartments a bad investments for speculators.