THE HOUSING CRISIS that created financial havoc for many small-business owners over the past two years may trigger a whole new raft of problems in 2009.

A recent report from the National Association for the Self-Employed, found that nearly 1.3 million business owners have already missed one or more mortgage payments. In the upcoming year or so, even more business owners are likely to follow in their footsteps. Roughly 23% of the 16.2 million self-employed small-business owners in the U.S. held risky mortgages in 2007, including adjustable-rate and interest-only loans, the report found. And many of those loans are due to reset to higher interest rates this year.

"We’ll see massive foreclosures and business bankruptcies," says Samuel D. Bornstein, a professor of accounting and taxation at Kean University in Union, N.J., and co-author of the report.

To help from falling to a similar fate, many homeowner-entrepreneurs have taken to moonlighting. While some simply rent out rooms to make some extra cash, others are embarking on consulting work or even starting up entirely new businesses, says Dave Vaughan, executive director of Neighborhood Development Services, a nonprofit homeownership-counseling service in Ravenna, Ohio.

Eric Coleman typically spends his days running his carpet cleaning and home-repair shop, Clean Carpet America, in Uniontown, Ohio. But these days he’s also spending several hours a week preparing tax returns from his home.

The former H&R Block employee turned to the side business after trying all sorts of ways to cut back on costs. He moved the carpet-cleaning business into his home, stopped eating out and, to save on fuel, only booked jobs when at least five rooms in a home need to be cleaned. But none of that was enough.

Once Coleman started doing tax returns on the side, however, things started looking up. Since he began moonlighting as an accountant last January, Coleman has earned an extra $30,000. "When the primary business is slow, this really helps in terms of making house payments and vehicle payments," he says.

Ross Marino, a certified financial planner who owns a Raymond James branch in Wilmington, N.C., had to substantially change his plans to expand his business when things started going south. Last year, he was determined to use his firm's two extra offices for new staff members and to build out the branch. Then revenues fell short. Instead of expanding, Marino became a landlord.

Now renting out those spare offices, Marino brings in an added $10,000 a year. He's also recognizing significant cost savings by postponing the company's expansion plans. “Over the next year or two it would cost me over $100,000 to staff those offices and put resources into it,” he says. “It would take 12 to 24 months before [I would] see a net return.”

Architect Neal Zimmerman, of Hartford, Conn., saw the writing on the wall as early as 2006. “Friends of mine who had only been doing residential [architectural] work were practically out of business,” he says. That’s when he started looking to diversify his revenue streams. Zimmerman expanded his reach beyond designing home offices and started designing prefabricated outdoor structures for residential use. The structures, which can be used for such things as a home-office, recreation area or guest cottage, sell for about $10,000 a pop. (Zimmerman plans to start selling them this spring). “My thinking is: now that people can’t flip their homes and move so quickly, they may need more space at less than the cost of building an addition,” he says. “People are afraid to spend money on anything right now.”

(For our story on how to make side businesses work, click here.)

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("Starting Up," a weekly column written by Diana Ransom for smSmallBiz.com, follows entrepreneurs through the early stages of launching a business. Write to her at dransom@smartmoney.com.)