if the band had a website, i'd cut them a deal on shirts that could be bought off that site. for the members, a shirt or two for free. i'd hit a couple of shows and give a few shirts away to some hotties willing to model them on the spot so i could snap a few pics for a blog. those girls may even wear the shirt again at some other gig. bands typically have sad, alcoholic female friends that hit their shows at least every now and then, so they're likely to buy it to support the band. selling shirts at a show is something i'd definitely do myself as everyone i know in a band is stoned and/or drunk by their second set. if the band is up for it, a free shirt goes to the craziest thing a girl will do onstage or a really quick karoake song with the band, basically a bunch of women screaming to be heard. or a giveaway for whatever reason.
i wouldn't go into the hole too much, though, and i would expect that everything i sold would *not* result in sales, one of those hope for the best, prepare for the worst scenarios. if nothing else, you should get into the show without paying a cover and likely will have a great time.
while you're there, that's a good time to talk to the bar owner or manager. these guys sometimes sell shirts with the bar's name on them, have staff or sponsor a pool, dart or softball team. if you can do banners, that might work out, too. it's not all just about the band and their drunken audience, try to make a couple of bucks and potential clients while having fun and staying relatively sober, in other words don't be a prude, but don't be mopping up your puke with your own t-shirts, either.
in all, i doubt there's going to much profit in it given the time invested unless you're lucky like mmoguls and hook up with a band that's serious about their music, though you can make some contacts in the process, sell enough to break even, and have a blast. it beats sitting around the tv on saturday night.
why don't strip clubs ever have live bands? that sounds like a riot....
