CNO Financial Group Inc., formerly Conseco Inc., will resort to a sealed-bid auction to unload the lavish Hilbert mansion in Carmel, which has been on the market for five years.

The estate was most recently listed for sale at $9.9 million—less than half of the original asking price and a third of the $30 million it was estimated to be worth in 2001.

"They're spending a bunch of money to take care of this thing, and they're not in the business of owning mansions," Prudential Indiana Realty agent Greg Cooper said of his Carmel-based client. Cooper is the listing co-agent for the property with primary agent Dick Richwine.

Bidders have until Aug. 20 to inspect the 40-acre property, and sealed bids will be accepted until 5 p.m. Aug. 27.

Conseco founder Stephen Hilbert had the 25,000-square-foot mansion at 1143 W. 116th St. built in 1993. The estate features a 15,000-square-foot "sports palace," guest house, catering facilities and power plant.

CNO won control of the 40-acre property during a court battle stemming from loans that Hilbert took out to buy company stock. The estate went on the market in 2005 at $20 million. Last year, the asking price was slashed in half.

Cooper said multiple would-be buyers have failed to close transactions. Given that history, he said bids will be evaluated for credibility as well as price. Complete terms of the sale are available at www.indianamansion.com.

Prudential will agressively market the property to affluent buyers worldwide. At the right price, Cooper said it could serve as a second or third home. Cooper said he has fielded multiple inquiries over the years from IndyCar teams. "We have some major events that go on here," he said.