Changes announced Friday to the administration’s Home Affordable Modification Program (HAMP) are expected to extend relief to a larger share of struggling homeowners as well as renters, according to federal officials.

One of the key adjustments to the program centers around principal reductions. HAMP currently includes an option for servicers to provide underwater homeowners who are struggling with their payments with a modification that includes a principal writedown.

To encourage investors to agree to principal reduction modifications, Treasury is tripling the incentives for such restructurings, paying from 18 to 63 cents on the dollar, depending on the degree of change in the loan-to-value (LTV) ratio.

The Federal Housing Finance Agency (FHFA) has prohibited Fannie Mae and Freddie Mac from employing HAMP’s principal reducing option for their borrowers. Treasury has notified FHFA that it will pay these same principal reduction incentives to Fannie and Freddie if they allow servicers to forgive principal in conjunction with a HAMP modification.

FHFA issued a statement in response noting that it recently released analysis concluding principal forgiveness does not offer any greater benefits than principal forbearance as a loss mitigation tool.

But the agency says it will reassess the investor incentives now being offered, taking into consideration the number of eligible loans, operational costs to implement such changes, and the potential effects of incentivizing borrowers to remain current.

Among the other changes announced, borrowers who are struggling because of debt beyond their mortgages, such as second liens and medical bills, will be eligible for an alternative program evaluation with more flexible debt-to-income criteria.

In addition, Treasury will expand eligibility to include investor properties that are currently occupied by a tenant as well as vacant properties slated for rental use.

Tim Massad, Treasury’s assistant secretary for financial stability says single-family homes serve an important function as affordable rental housing, and foreclosure of investor-owned homes has disproportionate negative effects on low- and moderate-income renters, as well as communities.

The deadline for HAMP will be extended for an additional year through December 31, 2013.

To date, HAMP has helped approximately 900,000 struggling homeowners permanently modify their mortgage loans, providing them with a median savings of more than $500 a month.

Massad says the administration is committed to a multi-pronged effort to support American homeowners and the housing market recovery.

In addition to foreclosure prevention initiatives such as HAMP, Massad says the federal government plans to focus on transitioning foreclosed properties into rental housing, making it possible for responsible homeowners to refinance, and providing hard-hit states with resources to develop targeted relief programs.

It is cheaper to buy a home than to rent one in 39 of the nation’s 50 largest cities, according to a quarterly report released today by real estate search and marketing site Trulia.

Trulia’s rent vs. buy index compared the median list price with the median rent on two-bedroom apartments, condominiums and townhomes listed on Trulia.com as of April 1, 2011, in the 50 most populous cities in the U.S. While 72 percent of the cities favored buying in the previous quarter’s report, 78 percent favored buying in this latest report.

“With home prices nearing a double dip and more foreclosures expected to flood the housing market over the next two years, the decision between renting and buying a home across most of the country has clearly moved in favor of buying,” said Ken Shuman, Trulia’s spokesperson, in a statement.

“As we head into the summer buying season, those looking to buy a home should be encouraged by improvements in the market and feel optimistic about their chances of finding an affordable home — much more so than in previous years.”