TPG's decision to explore a sale of RentPath comes amid soaring rents and lower vacancy rates in many U.S. cities. Rents have gone up more than 52.8 percent since 2000, while median household income has increased by just 25.4 percent, a study by real estate website operator Zillow Inc showed last month.

TPG, which bought RentPath for $525 million in 2011 from KKR & Co LP, is preparing to work with investment bank Moelis & Co to find a buyer, some of the people said, asking not to be named because the matter is not public.

TPG and Moelis declined to comment while a RentPath spokeswoman did not respond to a request for comment.

Formerly known as Primedia, RentPath provides digital classified advertising for apartment leasing and new home sales on several websites that it operates. These websites reach over 7 million unique visitors monthly, according to the company.

A potential sale of Norcross, Georgia-based RentPath would come on the heels of a deal for industry peer Apartments.com, which was sold to commercial real estate information services provider CoStar Group in March for $585 million.

A holding period by TPG of just three years would also be in sharp contrast to KKR's unprecedentedly long 22-year-long investment in RentPath, from its founding in 1989 to its 2011 sale to TPG. RentPath has transitioned from print publishing to operating websites as its advertising model changed.

In 2012, RentPath clinched a deal that made it the exclusive provider of multi-family apartment listings to real estate internet portal Trulia Inc. Trulia also sells display advertising and other media products on behalf of RentPath.

That partnership followed RentPath's $145 million acquisition earlier in 2012 of Rent.com from Ebay Inc, which it had in turn acquired in 2005 for $415 million.

Last year TPG paid itself a $110 million dividend by having RentPath borrow from banks, according to Moody's Investors Service Inc.

(Reporting by Soyoung Kim and Greg Roumeliotis in New York; editing by Andrew Hay)

By Soyoung Kim and Greg Roumeliotis