CHICAGO (CBS) — The single biggest investment for most Americans continues to take a hit. 

U.S. home prices have fallen by 4 percent over the past year, according to numbers released by the federal government Thursday. In the Chicago area, December figures show home prices hit their lowest levels since September 2006.

You might think the lower prices mean savings if you are in the market for a new home, but as CBS 2′s Vince Gerasole reports, you’d have to think again.

Mark Stolzenburg worked hard for his first home, a $430,000 three-bedroom condo. But the lawyer with stellar credit had to put 30 percent down — $130,000 — to qualify for the best possible loan.

“I guess that just goes to show how wide-ranging this recent mortgage crisis was,” he says.

For years, the standard down payment for conventional mortgages has been 20 percent. But Chicago is now one of nine U.S. cities where the median down payment required by banks has risen over the past three years to 22 percent.

Mortgage brokers know well the stories of banks denying loans as they ask for a greater financial commitment to the purchase. 

“Banks are looking to mitigate risk now. With the economic climate still shaky, they want buyers that have more skin in the game,” broker Justin Lopatin says.

Even a minor blemish on a spouse’s credit history can lead to a higher required down payment.

“A family with a good, healthy household income is disqualified from purchasing a home with 20 percent down, and that’s just unfair,” broker Dan Chookaszian says.

Real estate agents say the trend gives clients less purchase power and can turn off experienced buyers.

“It was so easy to get financing that first time, and now they feel like they are getting interrogated by the amount of documents they have to provide,” real-estate agent Paul Fortman says.

“I personally think it’s a good thing for our economy at large,” Chookaszian said. “I think it’s a difficult thing for me and my business.”

Brokers say when it comes to condominiums, banks are almost always asking for at least 25 percent down in Chicago — for homes, a bit less. There are federal programs out there that will allow buyers to purchase a home with as little as 3.5 percent down, but they are capped at $410,000 locally. When combined with mortgage insurance, they amount to higher overall monthly payments.