Billionaire Warren Buffett is preparing to auction off another private lunch to raise money for a homeless charity in San Francisco.

Over the past 18 years, Berkshire Hathaway's chairman and CEO has raised more than $26 million for the Glide Foundation through the annual auctions, the Associated Press reported.

Last year's winner got a relative bargain by paying $2,679,001 for the lunch. The record price for the auction is $3,456,789 that winners paid in 2016 and 2012.

This year's eBay auction starts May 27 and runs through 9:30 p.m. Central on June 1.

Buffett became involved with the Glide Foundation after his first wife, Susie, volunteered at the charity. She died in 2004, but the connection between Buffett and the group endured.

The winner can invite up to seven friends to join the lunch.