In relation to the general real estate market there is a general parasitic relationship between the real estate purchasing and apartment rentals. When the sales market is strong, and everyone is buying, the general rents that apartments can go for decline. As sales go down, and less people are buying, then then the rents on apartments go up.
People need a place to live, as such, there are only two options: to buy or to rent. This is true on a national, regional and local level but the effects are different per region. As housing grows scarce people will rent more and that will push the rentals to be more expensive. As housing grows more abundant the prices will trend downward and make purchasing more beneficial than renting an apartment.
