Samuel, 38, who also works part time as a security officer, now has about a dozen employees who collectively sit for an average of seven to 10 gigs per week.  Typical clients include busy professionals and executives along with people with out-of-town guests, who want to try popular items like Cronuts but whose hosts prefer to skip the wait.  Read MoreBest and worst tippers of food-delivery workers  The most interesting request so far?  "I had a Cronut delivery by a gentleman who wanted to deliver one Cronut to each of his girlfriends so I had to ask for two separate boxes—one Cronut each. One was going uptown. The other was going downtown. And he said, 'Please don't tell the other about the delivery,'" Samuel said.  He stressed the importance of being cordial and friendly to fellow line goers—in part to avoid the "instant amnesia" people can get when someone steps out of line to take a break and attempts to return.  Read MoreGodiva shelves some snobbery with soft serve  To drum up clients, Samuel relies on social media, word-of-mouth and Craigslist.  Competition comes mostly from Taskrabbits—a site where people post odd-job requests and offers—and other Craigslist posters. While there are line-sitting operations in Washington, D.C., that specialize in congressional and judicial hearing lines, there is little professional line service competition in N.Y.C.  "Once I have this up and running the way I want, and it's a very well-oiled machine, then I'll definitely consider branching out because there's a lot of opportunity," he said about expanding the business beyond the Big Apple. "There's a lot of impatient people, and there's so much to do and see and eat."
Impatience has a price. Professional line sitter Robert Samuel pegs it at $25 for the first hour and $10 for each additional half hour.