With more than a thousand stand-up shows competing for attention at the Edinburgh Fringe, the month-long residency can launch a career, or break the bank.
Comics need to stay in peak form this August, a task that this year is proving particularly challenging for Muslim comedians, since the festival coincides perfectly with the holy month of Ramadan.
For Imran Yusuf, a surprise hit last year, his prime evening slot means he's running almost on empty.
"I'm hard-core, I believe that the harder you make life for yourself, the more pain you can sustain," says the Kenya-born comic, whose show Bring the Thunder includes much discussion of his faith. "There's a great party scene here, great networking and schmoozing, but I don't really get involved in that. While I'm fasting I'll do my show, then I go out and have a decent meal, try to get some pasta down me. Then I go to my flat and have my tub of whey protein, a meal replacement shake, so I can have two meals in an instant and make sure I stay healthy because it's quite easy to get ill here."
Last year Yusuf became the first "free" performer to be nominated for one of the prestigious Edinburgh Comedy Awards (there are two offshoot free festivals, chiefly populated by new acts).
Hoping to follow in his footsteps on the free programme this year is Sadia Azmat, whose first Edinburgh show is a high-concept affair called Please Hold, You're Being Transferred to a UK-based Asian Representative. It is, as the title suggests, chiefly about her experiences in a British call centre, although it incorporates general material about race and religion. For Azmat, coming to Edinburgh also meant taking a lengthy break from her current call-centre position.
"I knew that Ramadan was going to fall," she says, "but when work was so kind to give me a month off, it was too good to pass up. In London, if you're not well known, you only get five or 10-minute slots, so this was the perfect avenue to do more of my material. I've been preparing for this for a whole year."
Azmat's show is in a less-desirable lunchtime slot, but audience figures have been healthy and a later gig such as Yusuf's might have been a struggle.
"I admire him, but he's skinny anyway - I'm chubby! If I don't eat, my stomach is going to tell me about it," she laughs. "I'm lucky - I don't have to change too much, I just stay up until sunrise, then do the prayer, then I wake up in the morning at about eight or nine and go over my lines."
"It does alter the Fringe experience slightly because if you can drink or eat you're a bit more relaxed. I might do a bit of networking towards the end of the run but I don't want to burn myself out. You have to pace yourself."
There are no refuelling issues for Nazeem Hussain and Aamer Rahman, who are making their Fringe debuts with the show Fear of a Brown Planet. Edinburgh is just one of numerous stop-off points for the Australian duo, and travellers can be excused from fasting - although they are required to make up the time later. They sympathise, though, with those struggling through the much longer days in the north.
"Twenty hours of daylight," says Rahman. "It's intense."
Designed to raise issues as well as laughs, their show highlights the concerns of brown people - as they put it - in Australia and the West. The mostly white crowd at the Fringe is novel for the duo, whose audience back home is primarily south-Asian. "The first couple of shows here we were thinking: 'Let's hope this works!'" admits Rahman.
It has so far, and Edinburgh crowds are generally more receptive than at regular club gigs. Have Hussain and Rahman suffered any adverse reactions back home? "We've had walkouts," says the latter, "but they're usually quiet. We usually don't have anyone bold enough to heckle us, as there are lots of brown people in the audience."
Yusuf, however, has suffered his fair share of abusive comments on the regular UK circuit. "I started comedy after 9/11," he explains. "People would shout 'Al Qaeda,' 'Taliban,' 'Check his shoes,' 'Suicide bomber.' You've just got to learn to take it."
The perseverance paid off, as after last year's Fringe breakthrough he embarked on a successful tour - happily devoid of racist heckles - and currently has a BBC TV show in the works.
The potential for nasty comments doesn't intimidate the newcomer Azmat, meanwhile, who already has "a thick skin" due to working at those call centres. It may just be the ideal day job for new comics contemplating Edinburgh. In fact, Azmat is confident of maintaining her stamina later in the run, despite the fasting.
"I talk for hours at work, 12-hour shifts sometimes, going: 'Hello, my name is Sadia' over and over again," she smiles. "It's nice to be here and just say my name once a day."