Over the last five years, renting has become progressively more expensive. According to commercial property tracker Reis Inc., the average US rent has increased 14% to $1,124 since 2010. This rate of increase is 4% points faster than inflation and more than double the increase in US home prices over the same period.

According to Hessam Nadji, chief strategy officer at Marcus & Millichap, a commercial real estate services firm, "The only relief in sight is rents in the hottest markets are going to go up at a slower pace, but they're still going to go up".

More people are now looking for apartments and this is the main reason behind the increased prices. According to Jed Kolko, chief economist at online real estate firm Trulia ,young people are looking for apartments after finding jobs as they prefer moving out from their parents' home after that. Many long-term renters are not planning for new home because of increased prices.

Moreover, most of the new apartments in the market are for affluent tenants and carry higher-than-average rents. This especially applies to cities, where new buildings are being increasingly built in urban core areas. This indicates that builders will have to get back to higher land and development costs.

According to Marcus & Millichap, in Denver, rents have increased over 5% a year since 2010; it became 9.2% in 2014. Last year, out of the 9,400 new apartment units, there were 23% in urban core areas.

This competition indicates that it would be difficult for renters to negotiate with landlords. They would also not be able to win concessions like a free month's rent.