MIAMI -

A Wisconsin man has put his kidney up for sale on Craigslist.

The man, identified only as Mark, said the highest bid he's gotten is $38,000.

"Right now, I'm at $38,000, the highest one. The other bid is $36,000," Mark said.

 Mark, who said he is a 49-year-old male, said he's willing to travel to South Florida to have the surgery done.

When asked if it was legal to pay for a body organ in the United States, Mark said, "It could be done in the States, but no one can know I'm getting paid. I could just be a donor."

In fact, we found plenty of people online willing to do the same, and it's illegal.

"It is becoming more of an issue," said Dr. Giselle Guerra, a transplant nephrologist at the University of Miami and the director of the Living Kidney Program in South Florida.

"In the United States, you cannot sell your organs, whether it be heart, lung, kidney or liver. That is the law," said Guerra.

This offense is punishable by up to five years in prison and a $50,000 fine.

Guerra said the donor/recipient relationship is investigated, in some cases for months, to make sure there is no money exchanged or material gain on the donor's part.

"You can't just show up and say, 'I'm John Doe. This is my friend. He's giving me his kidney. When can we start?' It doesn't work that way," said Guerra.

Kathy Ecklond, who has Stage 5 renal disease and spends five hours a day, three days a week on dialysis, placed an ad on Craigslist looking for a donor. She is on the transplant list, which is now 900 names long in South Florida.

Many of the responses have been from people looking for money.

One of them said, "Willing to donate my kidney for a sum." Another said, "Shouldn't be a problem if my needs are met."

Knowing it's against the law, Ecklond declined.

"They said,  'Well, I guess you don’t need a kidney bad enough.' I was very upset. I think it's despicable that they would prey on someone who is ill," she said.

Transplant centers like UM have measures in place to make it difficult to pull one over on the system.

Recipients and donors go through a series of interviews, evaluations and counseling that in many cases takes months.

"We have stopped donors. It won’t be the first time or last time it will happen," said Guerra.