I have met a lot of musicians and have read about musicians trying make gigs profitable. Some of them have told me to play for free.. wait what? I used to think that way too... and now the first thing I would tell you is to ask for what you are worth. Whats the worst that can happen? Not getting hired? Well that would be a good thing because you don't want to be hired at a gig that you don't receive payment. The venue and people will treat you poorly. HOW do I know this? Its because two years ago I performed in Coto De Caza at a house concert. I was treated like crap because they did not pay me. Imagine if you will it was 95 degrees out. The host would not allow me in the house ( I must have been some kind of animal or something) to cool down, and I had to change in this really bad smelling grotto like bathroom they had by their pool. There were other musicians, that they allowed in the house because they were paying for her, AND no cold water for me. Thank goodness I brought my own water and my gear. I am always positive and I did make a few connections that night.. but for the most part, it was insulting. It was the last time I decided to play for free.. unless it was a special circumstance, and it has to be a pretty amazing circumstance.
So before you say yes to a non paying gig, or a venue that wants you to bring in people to their venue. THEY should already have an established following of their venue. Always ask about the particulars, whether you can bring in your merch and sell it.
Most of all don't sell yourself short, because you are totally worth the money. Here is a fabulous article about this very subject:
Musicians and Venues, READ
Peace in Music