(Bloomberg) — The challenges facing prospective buyers of the least expensive homes in the U.S. are getting harder to overcome.

Already beset by stagnant wages, growing student debt and competition from investors who are snapping up listings, those looking to purchase moderately priced houses must also provide more cash up front. The median down payment for the cheapest 25% of properties sold in 2013 was $9,480 compared with $6,037 in 2007, the last year of the previous economic expansion, according to data from 25 of the largest metro areas compiled by brokerage firm Redfin Corp.

The higher bar is a symptom of still-tight credit that is crowding out first-time buyers even as interest rates remain near historical lows. Younger adults, who would normally be making initial forays into real estate, are among those most affected, weakening the foundations of the housing market and limiting its contribution to economic growth.