As more millennials look to leave their city rentals and become first-time homebuyers, roadblocks—like rising home prices and a shortage of housing—keep getting in their way. Adding to the obstacles: Over the past few weeks, the mortgage rate has been climbing and on Monday hit its highest rate in four years.

Last year, the average 30-year, fixed-rate mortgage was about 4 percent, according to CNBC. But that rate has climbed during the month of January, and by the end of last week, was up to 4.28 percent.

“On a typically priced American home, which is about $250,000, if the mortgage rate shifts even 0.5 percent, a monthly payment would go up by $70 and annually by $840,” National Association of Realtors chief economist Lawrence Yun told Newsweek.

According to Yun, consistent job growth and the strong economy could mean more millennials looking to enter the housing market this year, but increasing mortgage rates as a result of that same strong economy could spell trouble for those looking to buy their first home.