"If you have a $100,000 property and a $2,000 tax bill -- well good heavens -- no one's ever going to walk away from a $100,000 property for $2,000, if the value truly is $100,000 and the property is still standing," Westover, of the tax-lien association, said.

One risk with purchasing liens on distressed properties is that between the time an investor buys the certificate and the date they could foreclose, additional taxes and assessments can add up even as the value of the property may fall.

Some certificate buyers have seen their investments go underwater, meaning the value of the liens exceeds the value of the real estate, as property values have declined, said John Reid, an attorney with Tobin, O'Connor & Ewing in Washington.

"You're investing today on a lien-to-value ratio and hoping it either stays the same, or appreciates," Reid said.

Nationally, lien-to-value ratios average less than 10 percent, McOsker said. Those ratios may afford investors a margin of safety, yet tax-lien investors generally must pay off additional liens that have accrued on a property, such as for unpaid water bills, additional property taxes or related fees from the county or municipality, to complete a foreclosure, Waller said.

Liens for taxes owed to the IRS generally take priority over liens for property taxes in a bankruptcy, said Donald Dinan, a partner with Roetzel & Andress in Washington and general counsel for the association of lien investors. Homeowner bankruptcies generally halt the progress of foreclosures and can tie up investors' money for years, Reid said.

If there are multiple tax liens and multiple investors attached to a property, generally the buyer with the earliest certificate has the right to foreclose first, with rules varying by jurisdiction, Dinan said.

A certain portion of lien sales get voided after an auction because the taxes were improperly assessed, Reid said. In some areas, such as Washington, D.C., the jurisdiction pays the purchaser interest owed on voided certificates and in some, including most parts of Maryland, they don't, Dinan said.

Ruben Rodriguez, 37, who lives in West New York, attended the December auction and said he was there to learn.

'Safe Investment'