KENNY FUNK'S last three summers passed in a whir of beach days and kamikaze nights. There were Grateful Dead marathons and parties with 200 happy-houred guests stuffed onto decks made for 20. "The best times," he said.

He blames himself for this year. Instead of renting space in a beach share as usual, he and two friends decided to run a share house. This is like going from happy camper to camp counselor, or Eagle Scout to den mother. It's sobering, anyway. "The most overwhelming experience of my life," Mr. Funk said.

It was supposed to be fun. In shares, 20 or so adults -- 10 or so per weekend -- return to the ways of college life. It's share and share alike -- rooms, food bills, chores. Somebody or somebodies, namely the leaseholders, set the ground rules and make sure everything runs smoothly. In principle, this is fairly simple.

"Like the Fourth of July is the biggest beach weekend of the season," Mr. Funk said. "So the rule is everyone in the house could come, but no guests." A nice rule -- while it lasted.

"We've made exceptions," he said, after introducing two holiday guests lounging on his deck.

Fact is, juggling the hundred wants and needs of two dozen people is like trying to run across a floor full of marbles. You can make it, but watch out. Exceptions have ruled since he and his buddies laid out $20,000 to rent "Seaclusion," a five-bedroom bungalow camouflaged by pine trees and shrubs. They figured on renting 20 shares in this prime Fire Island community in no time. They would schedule the weekends, arrange maid service, set minimal rules. For the trouble, they would get free shares. But they were stymied from Step One.

"IT was really hard to rent the shares," said Mr. Funk, a 34-year-old graphic artist who lives in Manhattan. They began looking in March for compatible people with an ad in the Village Voice.

"At first, it was, like, really fun," he said. "We'd meet these three or four people at a bar on a Sunday and spend three hours drinking with them. We would tell them our interests -- Grateful Dead and whatnot. If we were lucky, they would call back and say for some reason or other they were going to another house."

This happened, he added, "about 20 times."

Mr. Funk's girlfriend, Nancy Goodman, said he began taking the whole share thing too seriously.

"It was beginning to affect our relationship," she said. "He couldn't stop talking about Fire Island. Whenever we got on the phone, the first thing he mentioned was the house. I told him I was really sick of this."

Until two weeks before the season started on Memorial Day, they still hadn't sold half the shares. "We thought we were going to have to shell out $3,000 each," Mr. Funk said. Luckily, people who I was in a house with before would wind up going into the house." With 24 people renting shares (most have quarter shares, or five weekends), 13 are people he knew.

"We ended up with full shares for $1,000," Mr. Funk said.

"But we really didn't want full shares," said Dave Barnett, one of his fellow leaseholders. "I don't really want to spend every weekend here."

They made big mistakes, Mr. Barnett added. "If people said they wanted blocks of time, we'd agree. We ended up giving weekends away."

THEY think the worst is over now. The house is working out pretty well. On Sunday afternoon, house members were lifting dumbbells off the deck, lounging on the deck, watching the sports channel in the living room, mixing drinks in the kitchen, listening to music in their bedrooms, waiting for a happy-hour party to start. The mix is 11 women, 13 men, ages 26 to 46.

"In our house," Mr. Funk said, "everybody gets along very well. It's a good mix. Everybody's a little nutty."

In a way, running a house has been a hassle because he doesn't like to make rules. There are shares with strict rules about who can visit when and what time you eat. "We really want to be loose," he said, ready for a happy-hour party in his "Faster Pussycat! Kill! Kill!" T-shirt and cutoffs. "We're not like camp counselors or mothers."

But he takes the big rules very seriously. "One of the cardinal sins of a summer share is that people in a house aren't supposed to date," he said. "The rule is A.L.D. -- After Labor Day." He admits he has committed the offense in the past. This year, he wouldn't let his girlfriend take a share in his house, even when he was desperate for renters.

"If you fight," he said, "it can ruin the house."

He worries. About how much fun people are having, whether the house is locked properly, how much toilet paper is left. On Saturday, he schlepped $100 worth of steaks and chops from Manhattan for a house barbecue "because food on Fire Island is so expensive." When a housemate complained that the ice maker was broken, he laughed. Then he frowned. "Does that mean I'm supposed to call someone about it?"