Perhaps it was a deal too sweet to be true, Marlene Arcos now reckons.

Arcos paid a man she met through an acquaintance more than $130,000 over a year to improve her home. He stopped working on the house this spring after tearing down portions of its roof and walls. County inspectors said he left it exposed to insect and rodent infestation and caused structural damage that will cost tens of thousands of dollars to fix.

Arcos, 56, of Silver Spring says she was defrauded by the unlicensed contractor, who failed to complete her new kitchen and make additional structural improvements.

"What I've gone through this year has been a nightmare," said Arcos, standing outside her unfinished residence, which Montgomery County officials used yesterday as a backdrop to announce a crackdown on unlicensed home improvement contractors. "It caused me great emotional pain and financial damage."

Home improvement scams are on the rise in Montgomery County as the price of real estate continues to climb and homeowners shop for deals to expand or repair residences, county officials said. The county's Department of Housing and Community Affairs has received 58 complaints of shoddy work by unlicensed home improvement contractors this year; in 2004, it received 47.

County officials say senior citizens and first-generation immigrants appear to be especially vulnerable to home improvement scams. The housing department recently created a position for a bilingual investigator.

County leaders say they've fought back by filing criminal charges against unlicensed contractors in 24 recent cases to resolve disputes that are more commonly settled in civil court.

"If you're here to rip off our homeowners, we're going to track you down and prosecute you to the fullest extent of the law," Montgomery County Executive Douglas M. Duncan (D) said after walking around Arcos's house trailed by television cameras.

Prosecutors have obtained six convictions and have issued eight outstanding arrest warrants against shoddy contractors in recent years. Three are awaiting trial. Deputy State's Attorney John J. McCarthy said his agency could not immediately determine how many it has prosecuted criminally in recent years. He said prosecutors are seeking tougher penalties, citing a recent case that resulted in a nine-month sentence.

Arcos's contractor, Milton O. Hernandez, 37, of Silver Spring, was charged with doing home improvement without a license, failure to complete work and theft. He pleaded guilty last month to failing to finish the work and agreed to reimburse Arcos in $700 installments, to be paid monthly. Neither he nor his attorney could be reached yesterday.

But even when authorities win cases against unscrupulous contractors, restitution can be slow and painstaking for victims. Arcos, an Ecuadorean immigrant and single mother who cleans houses for a living, said she has not seen a penny of the money she paid the man, which she got through a loan.

"I'd like to see stiffer penalties for something like this," Duncan said.

County officials urged homeowners who are considering hiring contractors to consult with the state Department of Labor, Licensing and Regulation. The agency's Web site is www.dllr.state.md.us, and its phone number is 410-230-6309.