Why would people use his property to park cars? The developer would purchase property and include a driveway / garage. You are being ridiculous. The problem is that regulations wouldn't allow an 8 family home. I live in a dense area and there are single families, triple deckers, and apartment complexes all around me. Welcome to Boston
If 8 families want to live in a single family home, it must be an exceptionally desirable area, with very little housing.
It stands to reason there are probably many more people who want to move in to the area, but who aren't willing to be one of 8 families in a single family home.
So given the huge amount of pent-up demand, there must be some building laws in place keeping this specific city from growing upwards, and generating supply for this demand.