A 'sale pending' sign is displayed in front of a home for sale May 24, 2010 in San Rafael, California. (Justin Sullivan/Getty Images)

The index measuring pending home sales rose 5.2 percent in July compared to June, according to the latest survey by the National Association of Realtors (NAR).

The news was deemed to be positive by investors last Friday. But the trade organization tempered the optimism, saying that more affordable homes can help sales, but without federal tax credit help, sales are destined to be slow. "Home sales will remain soft in the months ahead, but improved affordability conditions should help with a recovery," Yun said in a NAR statement.

The news helped stocks of home builders gain last Friday. The SPDR S&P Homebuilders exchange-traded-fund, which measures the performance of companies in the home building sector, gained 2.7 percent.