* Tough state immigration crackdown starts on Thursday

* Boom in yard sales as migrants sell off belongings

* Legal residents, US-born children join scramble to leave

PHOENIX, July 25 (Reuters) - Nicaraguan mother Lorena Aguilar hawks a television set and a few clothes on the baking sidewalk outside her west Phoenix apartment block.

A few paces up the street, her undocumented Mexican neighbor Wendi Villasenor touts a kitchen table, some chairs and a few dishes as her family scrambles to get out of Arizona ahead of a looming crackdown on illegal immigrants.

“Everyone is selling up the little they have and leaving,” said Villasenor, 31, who is headed for Pennsylvania. “We have no alternative. They have us cornered.”

The two women are among scores of illegal immigrant families across Phoenix hauling the contents of their homes into the yard this weekend as they rush to sell up and get out before the state law takes effect on Thursday.

The law, the toughest imposed by any U.S. state to curb illegal immigration, seeks to drive more than 400,000 undocumented day laborers, landscapers, house cleaners, chambermaids and other workers out of Arizona, which borders Mexico.

It makes being an illegal immigrant a state crime and requires state and local police, during lawful contact, to investigate the status of anyone they reasonably suspect of being an illegal immigrant.

The U.S. government estimates 100,000 unauthorized migrants left Arizona after the state passed an employer sanctions law three years ago requiring companies to verify workers’ status using a federal computer system. There are no figures for the number who have left since the new law passed in April.

Some are heading back to Mexico or to neighboring states. Others are staying put and taking their chances.

In a sign of a gathering exodus, Mexican businesses from grocers and butcher shops to diners and beauty salons have shut their doors in recent weeks as their owners and clients leave.

On Saturday and Sunday, Reuters counted dozens of impromptu yard sales in Latino neighborhoods in central and west Phoenix/

“They wanted to drive Hispanics out of Arizona and they have succeeded even before the law even comes into effect,” said Aguilar, 28, a mother of three young children who was also offering a few cherished pictures and a stereo at one of five sales on the same block.

She said she had taken in just $20 as “everyone is selling and nobody wants to buy.”

LEGAL RESIDENTS FLEE

Arizona straddles the principal highway for human and drug smugglers heading into the United States from Mexico.

The state’s Republican governor, Jan Brewer, signed the law in April in a bid to curb violence and cut crime stemming from illegal immigration.

Polls show the measure is backed by a solid majority of Americans and by 65 percent of Arizona voters in this election year for some state governors, all of the U.S. House of Representatives and about a third of the 100-seat Senate.

Opponents say the law is unconstitutional and a recipe for racial profiling. It is being challenged in seven lawsuits, including one filed by President Barack Obama’s administration, which wants a preliminary injunction to block the law.

A federal judge heard arguments from the lawyers for the Justice Department and Arizona on Thursday and could rule at any time.

The fight over the Arizona law has complicated the White House’s effort to break the deadlock with Republicans in Congress to pass a comprehensive immigration law, an already difficult task before November’s elections.

While the law targets undocumented migrants, legal residents and their U.S.-born children are getting caught up in the rush to leave Arizona.

Mexican housewife Gabriela Jaquez, 37, said she is selling up and leaving for New Mexico with her husband, who is a legal resident, and two children born in Phoenix.

“Under the law, if you transport an illegal immigrant, you are committing a crime,” she said as she sold children’s clothes at a yard sale with three other families. “They could arrest him for driving me to the shops.”

Lunaly Bustillos, a legal resident from Mexico, hoped to sell some clothes, dumbbells and an ornamental statue on Sunday before her family heads for Albuquerque, New Mexico, on Monday.

“It makes me sad and angry too because I feel I have the right to be here,” said Bustillos, 17, who recently graduated from high school in Phoenix. (Editing by John O’Callaghan)