Borrell Associates told MediaPost that it predicts real estate online advertising spending will increase 55 percent in 2005 to $1.8 billion. Borrell believes that online spending across categories will grow to $11.2 billion, putting the real estate share at about 16 percent at the end of this year, compared to only about 10 percent at the end of 2004.

Sticking its figurative neck out, Borrell predicts that online marketing for real estate will outweigh even the real estate ads in newspapers by 2009.

Big advertisers in the field, not surprisingly, are brokerages and agents. They tend to pay up to $2 a click, although some hot markets see clicks rising to $3 and $6 and even more.