MISSOURI CITY, Tex. — Look closely and it is there, sandwiched between Goldman Sachs Hedge Fund Partners II and D3 Family Bulldog Fund: the mortgage on Timothy and Betty Stamps’s modest home on Gentle Bend Drive here.


Nearly lost among the blizzard of hedge funds, thoroughbred horses and other gold-plated investments in Mitt Romney’s personal financial disclosures, the interest from the $50,500 mortgage is loose change to Mr. Romney, whose net worth has been estimated at close to a quarter-billion dollars.


Yet for the Stampses, who have been writing $600 monthly checks to “Willard M. Romney” for 15 years, the money they borrowed from him to buy their home in 1997 was life-changing.


The mortgage is the last vestige of a troubled, and previously unreported, investment by Mr. Romney in Texas real estate in 1982, before he struck it rich as the wunderkind of Bain Capital. And while the Stampses’ happy ending is a counterpoint to the image, seized upon by political opponents, of Mr. Romney as a cold, calculating financier, the episode also offers an early illustration of his appetite for deals promising low risk and high return.


Lured by the prospect of buying five rent-to-own houses in the Houston suburbs without putting up any of his own money, Mr. Romney jumped into a speculative deal geared toward “affluent free enterprise capitalists who desire a quality investment with tax shelter benefits,” according to a prospectus. Based on frothy assumptions of a never-ending real estate boom, it was unlike the data-driven, analytical investments that came to define his later successes at Bain Capital.


The result was a rare Romney flop: The housing market soon collapsed, and he was stuck renting out the houses for years before unloading them, mostly at a loss, in the late 1990s, according to property records. The renters were offered the first chance to buy, but the Stampses could not qualify for a mortgage, recalled Mr. Stamps, who at the time had recently lost his job at an oil company.


“Then I got this phone call, personally, from Mr. Romney, asking if we really wanted to buy the house,” Mr. Stamps, 63, said in an interview the other day at the barbershop he now runs. “I said, yes we did. And he said he would loan us the money. He really helped us when we needed it.”


Amid the campaign furor over Mr. Romney’s wealth and taxes, the relatively tiny real estate investment — the mortgage generates less than $2,500 in annual interest income, according to his disclosures — has gone largely, though not entirely, overlooked.


Mr. Stamps said that he and his wife had received calls in recent months from strangers who “seemed to be looking for negative stuff” about Mr. Romney, but that the couple had nothing to say to them. (The Stampses recently refinanced the original 30-year loan; the new mortgage, still with Mr. Romney, was dated June 12 but signed just two weeks ago. Details of the interest rate were not included in the public record.)


Andrea Saul, a Romney campaign spokeswoman, declined to answer questions about the Texas investment.


At the time Mr. Romney made the investment, he was a rising star at Bain & Company, the management consulting firm, and was still a couple of years away from starting Bain Capital, its private-equity spinoff. Real estate speculation was rampant in Texas, and William Roy Jolly, an airline pilot and investor from Utah who knew Mr. Romney through the Mormon Church, approached him about investing in a deal to buy new low-to-middle-income houses at a discount.


The deal, Mr. Jolly said, was “a marvelous scheme” to help renters who could not qualify for a mortgage to eventually buy their houses, while allowing investors to write off depreciation and mortgage interest on their taxes without risking their own money: most purchases were 100-percent financed with first and second mortgages from Texas banks.


The prospectus for the investment, called the Gem Plan, played up the tax shelter benefits, saying it was structured “so that deductions are projected to be twice the amount of the cash required each year.”


Mr. Romney elected to buy five houses, intending that the profits would accrue to each of his five sons, Mr. Jolly said.