There will be times when you'll be asked to play for free. There are some good reasons for playing gratis, and only you and your bandmates can decide how to handle it. Well, then, just how do you decide whether you are going to do a job when there's no money to be had. In short, WIIFMAMB (What's is in it for me and my band)?
Sucker Play
The first question I like to ask is, “Who else is working for free?” Too often the answer is “Just you.” That's when I have to ask some serious questions.
Experience
If you're at the stage where you're desperate for experience, then go ahead and latch on to any chance to play -- friends' parties for example. Also get out to open stage nights and do a few guest sets. But once you feel comfortable in front of an audience, you may want to move on to the next stage: actual gigging ... for pay.
Exposure
The so-called showcase is presented as an 'opportunity' to get your music in front of people who can help you move forward, often augmented by the opportunity to promote the event and sell tickets to 50 of your friends. Sadly, the chance that a person of influence will hear you and then seek you out may be no better than at a paying gig. The exception is if you'll be paired with a major name. Appearing with or opening for a top local or up-and-coming band can be a good step toward more gigs.
Good Works
If I'm going to support a charity function, I want to know what my time and effort will be going toward. If a charity really means something to me, then I may leap at playing at their fund-raiser. It’s a bonus if the charity complements my 'branding'. It also doesn't hurt if the event has a high profile (see Exposure).
Credibility
In this business, you're only as valuable as your perceived worth. If you have a reputation for wantonly giving away your services, you may not gain the respect of other musicians or the people who could hire you.
So playing for free might be a good move ... depending. Many artists choose to do a set number of charity gigs each year. Just understand that a freebie has the potential for both enhancing or hampering your career.