Supply and demand are key factors in pricing. If no one wanted to buy houses, prices would go down. Of course, people foolishly want to live in dwellings rather than under bridges, so there will always be some amount of demand. Therefore, increasing the number of dwellings will have an impact on both rental prices and house prices. People can still charge whatever they want for their house, but if there is something more desirable for a lower price, it isn’t going to sell. Likewise for rental properties, landlords want to make as much as possible, but vacant units bring in less money than units with reduced prices. Again, that only matters when there is a sufficient supply of residences for the population.