There’s nothing exceptional about the boxy-looking two-family at 13 Essex Street in Revere, Massachusetts.

What is remarkable is the story behind a subprime-mortgage deal that allowed a lab assistant making about $36,000 a year to buy the property with $670,000 in loans.

As real estate and federal court records show, Marielite Hardy never made a mortgage payment after buying the two-family house in March 2006. The tale of her mortgage illustrates how the subprime crisis was caused, in part, by a web of relationships that included Wall Street, big national banks, and unscrupulous mortgage brokers.

The case is a reminder of what precipitated the collapse of Lehman Brothers a year ago and touched off a global economic crisis that has drawn comparisons to the Great Depression. With no system of checks and balances, borrowers with weak credit got easy money from banks that waited too long to ask the tough questions about their subprime customers.

Hardy could not be reached for comment. Her mortgage was a so-called no-documentation loan that allowed her to borrow a large sum of money without requiring her to provide any record of her income.

The lender, First Franklin Financial Corp., later learned Hardy’s income was about $3,000 a month, not the $12,000 per month stated on her loan application, court records show.

When First Franklin made the loan to Hardy, it was part of Cleveland-based National City Corp. To spur growth and profit in areas outside its core footprint, the bank relied on an army of mortgage brokers to drum up business. The strategy backfired for National City and many other banks because they didn’t have a handle on how lax the loan underwriting had become at mortgage broker outposts across the country.

The loan to Hardy, however, did not necessarily have to be First Franklin’s problem. Shortly after closing on Hardy’s mortgage, First Franklin sold her loans to HSBC Securities Inc. in the secondary market. Hardy’s mortgage then was destined for securitization, a process in which Wall Street bundled thousands of loans together and then sold them as investments to hedge funds, pension funds, insurance companies, and other banks.

But because Hardy never made her scheduled mortgage payments, her loan was prevented from becoming part of a mortgage-backed-securities offering.

Instead, HSBC demanded that First Franklin repurchase the loan.

First Franklin took back the loan. And to cut its losses on the Revere mortgage, the San Jose, California-based lender sold Hardy’s loan in a distress sale on December 30, 2006, court records show. First Franklin took a loss of nearly $300,000 on the deal. Meanwhile, that same day, Merrill Lynch paid National City $1.3 billion to acquire First Franklin.