Prosper Marketplace wants to find investors to finance your fertility treatments, weight-loss surgery and new teeth.

The online lending platform, which arranges funding for unsecured consumer loans, announced its first takeover Tuesday, paying $21 million to buy American HealthCare Lending LLC. The target offers loans for elective medical procedures including dentistry, bariatric and spinal surgery, mental health programs and hospital stays. Its website says debts can reach $100,000.

"It's going to be an important driver of growth," Prosper Chief Executive Officer Aaron Vermut said in an interview. Over time, "if we execute this correctly, we could be originating in the billions of dollars of loans in this space a year."

Consumers are turning to online platforms run by Prosper and larger rival LendingClub Corp. to consolidate debt, finance home repairs, make purchases and in some cases cover health-care costs. While San Francisco-based Prosper originated $1.6 billion in loans last year, a more than three-fold increase from 2013, less than 10 percent was for medical procedures.

Prosper's main offerings are unsecured consumer loans for as much as $35,000 and as long as five years. Borrowers request money online, Prosper vets applications, and individual and institutional investors pledge funding. Interest rates are often lower than the cost of carrying a credit-card balance.

The model gained attention last month as LendingClub sold stock to the public, briefly gaining a valuation of more than $10 billion as shares almost doubled from their offering price. The stock slid about 21 percent this year through Monday. LendingClub expanded in medical loans last year through its purchase of Springstone Financial for $140 million. It also provides small-business loans and some funding for education.

Patients access American HealthCare's cloud-based platform from a doctor's office, at home or on a mobile phone. The Salt Lake City-based firm's website says patients or family members can submit an inquiry in less than two minutes, and loans can be approved in seconds. Terms last as long as seven years.

Prosper already finds investors for about two-thirds of American HealthCare's loans, focusing on prime borrowers whose requests are within its maximum loan size. Prosper either finds funding for whole loans or uses its fractional channel, offering investors portions of debts in $25 increments.

Some medical lenders use systems similar to credit cards. Prosper aims to compete by offering lower rates, funding the debts through its peer-to-peer platform, Vermut said.

Almost half of the financing American HealthCare Lending arranges is for fertility treatment, he said in the phone interview. Prosper wants to fund more weight-loss treatments and surgeries to improve vision, he said. It may choose not to arrange loans for some elective surgeries, he said, without elaborating.

Prosper's backers include BlackRock Inc., Sequoia Capital, Francisco Partners, Institutional Venture Partners and Phenomen Ventures. In its last round of fundraising in May, the company was valued at about $650 million, a person familiar with the matter said at the time.