No one is advocating a return to the lax lending standards of 2006, when buyers with no income or documentation could get loans. But many people say they believe lenders and the government, in correcting the excesses of that era, have gone too far in the other direction.

Fannie Mae, the government-controlled company that buys mortgages, is so dominant in the lending market that its rules set the standard. It recently toughened its policies, saying it would count only 70 percent of the value of stocks and mutual funds when calculating a buyer’s assets. Previously, that figure was 100 percent.

A Fannie spokesman, Brian Faith, said tighter regulations screened out those unprepared to be owners.

“One of the important lessons learned in the past few years is that it is not enough to help a borrower own a home,” Mr. Faith said. “We must also help ensure that they will be able to stay in the home over the long term.”

Mortgage brokers say those who are being rejected for loans are often entrepreneurs who are used to taking risks. “They are chomping at the bit to get into this market, but are forced to the sidelines,” said Stuart Fraass of Guaranteed Rate Inc. “If you’re self-employed, you have virtually no chance of getting a mortgage now.”

Mr. Fraass was unable to help Raghbir Singh, a real estate investor who owns a gas station in Dover, N.H. Mr. Singh tried to buy a $301,000 house for himself and his family with 10 percent down and excellent credit, but was rejected. “It was unfair,” Mr. Singh said. “I’m a good risk, but I’m forced to rent.”