More than 14 million American households spend more than half their income on housing, according to the Harvard Joint Center's 2003 State of the Nation's Housing report. For the first time on record, more of these cost-burdened households are owners (7.3 million) than renters (6.9 million). The major reason: Those 55 and older are maintaining mortgage debt at higher levels and for longer than in the past, but 2.7 million households that own their homes outright are also seeing higher housing expenses thanks to increased property taxes and other costs.