The Census Bureau's recently released biennial American Housing Survey is a treasure trove of interesting stuff about the country's housing stock. The report, sponsored by the Department of Housing and Urban Development, contains facts and figures like the number of U.S. homes that have more than two bathrooms or more than four bedrooms. But it's also chock full of fascinating categories with mortgage implications.

Lenders interested in finding borrower leads for home equity loans or lines of credit should be interested to learn that more than one-third of all one-to-four family, owner-occupied houses are owned free and clear. Even more interesting to reverse mortgage lenders is that more than half of those free-and-clear homes are owned by seniors.

The survey (a sample that's extrapolated to estimate all of U.S. housing) doesn't provide names or addresses of potential leads; originators will have to find those for themselves. But knowing how big the universe is will be valuable when they decide what types of lending are worth taking on.

So, of the 76 million owner-occupied units in the United States (an estimate, as are all these numbers), 27 million of those owners have paid off their mortgages. Of that 27 million, 14 million are owned by seniors.

About 6% of owner-occupied homes are manufactured housing (4.5 million), and 1.8 million were built in the most recent four years from 2013, or about 450,000 per year.

Just 421,000 of the 76 million total units currently have a reverse mortgage on them, while only 6 million have a home equity loan — indicating the untapped capacity for these loan products is immense.

Interested in mortgages opportunities with minority borrowers? Approximately 6 million blacks and 7 million Hispanics own homes, or about 18% of the 76 million total. In addition, about 2 million houses are owned free-and-clear by blacks, and another 2 million by Hispanics, which represents about 7% each of the overall population of homes owned free-and-clear.

The American Housing Survey can also be analyzed by region or metropolitan statistical area. For example, 17 million owner-occupied units, or about a quarter, are in central cities. And that's just scratching the surface — there are 17 other interesting categories.

Ever wondered what the age is of the oldest still-active mortgages? There are 226,000 borrowers with mortgages made between 1970 and 1974. Who knew there were so many 40-year mortgages? (The median mortgage term, by the way, is 30 years, indicating the enduring appeal of the 30-year mortgage.)

The median interest rate is 4.5%, with a median remaining principal balance at $122,000. About 4 million people are at or near jumbo mortgage range, owing more than $300,000 on their loans.

Looks as if there's still a lot of need for mortgage insurance, too, as 12.5 million have mortgages with loan-to-value-ratios above 80%. The median LTV, though, is below MI range, at 70%.

Median mortgage payment is an affordable $999 per month. Perhaps surprisingly, the largest number of owners, about 7 million, fits into a fairly affordable range of $500 to $749 per month, with another 7 million borrowers in the next highest payment amount category, $749 to $999.

Some 5 million owners have debt-to-income ratios above 40% — and that's just mortgage debt — meaning a significant number of owners would be non-qualified mortgages if they had to refinance right now.

The Census Bureau touts the American Housing Survey as "the most comprehensive housing survey in the U.S." The sample size is 57,700 housing units.

Oh, and of the 133 million total housing units in the country (owner-occupied or otherwise), just a hair above 50% of them have two or more complete bathrooms.

Mark Fogarty, Editor at Large at National Mortgage News, brings more than 30 years of experience to his analyses of the mortgage market.