Medical debt is the single biggest cause of bankruptcy in America. For Marlena Wilzbach of McKinney, it could end up taking her family home.

Wilzbach and her husband, Mark, are putting their home on the market to pay for an expensive surgery to repair a spinal injury suffered in an auto accident. The cost of the surgery: $300,000.

Her medical debt saga began in April 2016 when the driver of a truck ran a red light and sped into the passenger side of a minivan Wilzbach was driving. It was filled with carpooling kids, including one of her daughters.

"I twisted [the wheel] as hard as I could and saved my daughter's life," she said.

Wilzbach took the brunt of the head-on impact. She now has a severe spinal injury that makes each step a struggle. Doctors said she needs an invasive back surgery to have any hope of normal mobility.

Her husband is self-employed with no medical insurance. The man who smashed up the family's minivan is unemployed with no assets and no insurance. Her insurance gave her a $20,000 payout for uninsured motorist coverage.

"We're screwed. We're financially behind the eight ball and the only financial asset we have is our home," said Mark Wilzbach.

So they made the difficult decision to sell the home to pay for her surgery. But they first needed to make improvements to get the most out of the home. A dispute with a contractor making the repairs is adding extra stress and causes Wilzbach to tear up as she described her family's plight.

Marlena Wilzbach goes over medical bills with an NBC5 consumer reporter. (KXAS-TV (NBC5))

Mary Spector, who runs the Civil Clinic at Southern Methodist University, has worked with families like the Wilzbachs for 20 years. Many times, she said, it doesn't take a debilitating accident or illness to put a family into unsurmountable debt.

"Insurance companies, medical providers, hospitals, doctors, labs. From one visit to the emergency room, you can have four different creditors trying to collect their portion of the debt," Spector said.

Medical debt is assigned interest and can grow every day it goes unpaid. When medical providers give up on getting paid, they'll often sell outstanding debt to collectors who buy it for a fraction of what is actually owed.

A debt collector can buy $1,000 in outstanding debt for just $10. Not only can they still charge you the full amount, but they can add more interest and even take you to court.

Texans dealing with that debt are terrified, Spector said.

"They're worried to pick up the phone, they're worried to answer the door, they're worried to pick up the mail, they don't know what their rights and responsibilities are and so they're fearful," she said.

Since medical debt is one of the biggest complaints received by KXAS-TV (NBC5)'s consumer team, the station spent $20,000 to buy $2 million in outstanding medical debt for 2,000 North Texas families. Those families will receive letters notifying them that NBC5 is forgiving their debt. The station was unable to ask for the debt of specific families, like the Wilzbachs.