More Americans signed commitments in April to buy existing homes, the third consecutive month that the housing market saw an increase, according to numbers released today by the National Association of Realtors (NAR). The Pending Home Sales Index, which measures consumers’ intentions to buy homes, rose 6.7 points to 90.3, up from a reading of 84.6 in March.

At the same time, the NAR’s Housing Affordability Index suggests that buyers will have the means to follow through on their word. The index rose to 174.8 in April, from a reading of 171.9 in March. It was the second-highest monthly reading on record, after it peaked at 176.9 in January, the NAR said.

Record low mortgage interest rates, combined with first-time buyer tax credits drove the changes, according to the NAR. “Housing affordability conditions have been at historic highs, but now the $8,000 first-time buyer tax credit is beginning to impact the market,” said Lawrence Yun, chief economist for the NAR. “Since first-time buyers must finalize their purchase by November 30 to get the credit, we expect greater activity in the months ahead.”

Although the numbers suggest improvements to housing sales, Yun’s outlook for the next few months remained cautious. Although the total number of existing home sales is expected to improve overall, the NAR expects dramatic variations by local markets. “The market has already bottomed in some areas, but this is an unusual housing cycle,” Yun said.

Financial planners, similarly, had a measured reaction to the numbers. “The housing market is not going to be the engine leading us out of the recession,” said Bill Ramsey, principal of Raleigh, N.C.-based Financial Symmetry. “But clearly it is going to be less of a drag than it has been or should be.”