A new study from Fannie Mae suggests that many Americans fail to do their homework when considering mortgage options, creating problems for both borrowers and lenders.

According to the GSE’s November National Housing Survey Topic Analysis Report, many borrowers may be missing out on savings when it comes to shopping for mortgages, largely because of a lack of understanding about what’s available. This leads to increased costs and sometimes creates problems during the life of the loan.

“Although a home purchase is the largest financial obligation most people will ever make, many borrowers do not fully understand their mortgage products and costs,” said Doug Duncan, chief economist at Fannie Mae. “As a result, some homeowners in this position may find themselves with unsustainable payments down the road.”

The problem is especially prevalent among lower-income respondents (defined in the survey as households earning $50,000 or less per year). Forty-three percent of low-income respondents said they obtained an offer from only one institution when shopping for their current mortgage—a full 10 percentage points more than high-income respondents (households earning at least six figures annually).

Research done for HUD indicates borrowers who fail to shop around may be missing out on $1,000 or more in savings on closing costs.

While lender reputation seems to be an important factor for borrowers across all income groups—at least two out of three respondents in each income bracket say it is a major consideration—low-income consumers are more swayed by real estate agents and mortgage brokers when choosing a lender. They are also less likely to factor in the competitiveness of their offers: 54 percent of low-income respondents cite competitiveness as an important factor, while 76 percent of high-income respondents say it is a major point for them.

In addition, high earners appear to be more comfortable shopping around using technology. Half of low- and mid-income respondents say they obtained the quote on their mortgage in person, while more than 60 percent of high-income shoppers got their quote over the phone or on the Internet (through either their lender’s website or a third-party comparison website).

Moreover, high-income respondents expressed greater comfort with the idea of using their mobile devices to research homes, lenders, and rates. However, respondents across all income groups still seem reluctant to actually obtain a mortgage product on a mobile device, with less than a quarter of each group saying they would be comfortable doing so.

Another common thread among consumers of all income brackets is their failure to understand key mortgage elements. When asked to estimate the maximum percentage by which the monthly adjustable-rate mortgage (ARM) payment can increase over the life of the loan, 41 percent of respondents were unable to answer.

Among those who actually offered an estimate, the average guess was around 10 percent, well short of Fannie Mae’s calculation of more than 50 percent.