Laura Towery and Debbie Conway of DeLa Designs shooed painters out the back door of Sotherby Homes’ house as the six judges for the Parade were coming in the front door.

The day before, a furniture supplier had failed to show up with the promised furniture for a bedroom and the game room. Again the designers saved the day by stripping out their personal furniture, including Ms. Towery’s bed, for the rooms.

These are but a couple of the last-minute hurdles after nine months and thousands of hours of planning, creativity and attention to detail required to make Sotherby’s house the gold medal winner for the best interior design at the Parade of Homes.

A piece of someone else’s backyard. Home sites with no water, power or sewage. Hilly desert acreage, miles from the nearest road. A one-thousandth share of a building. Parcels in the middle of the street. Building lots under 10 feet of Candlestick Point water.

It’s the world of tax auctions, where government agencies sell real estate they’ve seized from owners who have fallen far behind in their property taxes. In California such duties fall to county tax collector’s offices, which each year place hundreds of parcels that are in arrears at least five years on the block.

“Folks, take advantage of the market today,” a fast-talking auctioneer exhorted a packed room of real-estate bargain hunters on Sunday. “I have (a bid for) $300,000 now on this condo; do I hear $310? I’ll take $305 if that’ll help you. Who else wants in? Raise those bidder cards.”

The bidding got fast and furious, and the three-bedroom condo in South San Francisco sold for $425,000.

It was among 88 foreclosed properties, mostly in Alameda, Contra Costa and Solano counties, auctioned at the San Mateo County Event Center.

Sales of existing homes fell for a third straight month in May, dropping to the lowest level in four years as the median sales price declined for a record 10th consecutive month.

In a troubling sign for the future, the inventory of unsold homes shot up to the highest level in 15 years, meaning more downward pressure on prices in the months ahead until the inventory glut is reduced.

Sales fell by 0.3 percent in May to a seasonally adjusted annual rate of 5.99 million units, the National Association of Realtors reported Monday. Sales now stand 10.3 percent below where they were a year ago.