Together with some friends, I helped start a rock/blues band in Chicago many years ago. We had this idea that we would play charity events for local homeless shelters, food pantries, etc. We didn't intend to make any money on the project. We put the band together, wrote about an hour's worth of original material, rehearsed, and then contacted several local charities.
To our surprise, we found that they weren't interested. We said, "You host an event, we'll provide entertainment, and you take any and all of the money. You don't pay us anything." They didn't want to do it. We talked to some local coffee houses and churches who finally agreed to let us use their locations for such an event. Flyers were printed (or photocopied) and distributed, and we got to play.
One event, however, was a complete disaster. I booked a coffee house in Chicago's North Loop area for the weekend between Christmas and New Year's day. They had performers in on a weekly basis and were confident this would work well. The place was on the 2nd or 3rd floor (narrow back stairway) with no signage out front. We were booked for Friday and Saturday night. Friday night, a massive snow storm hit. We outnumbered the crowd. No money raised that night.
Like complete and utter morons, we came back for the second night. Based on our incessant whining, our families came to support our efforts. Bolstered by this upswing in attendance, we played our gig. The manager of the coffee house was much happier and speculated that we had earned "a few dollars" for our designated charity.
No one ever got the money. The charity never got it. We didn't get it. We spent hours trying to get home in the blizzard after that event. Our sax/vocalist and his wife were locked out of their house and spent the night on my couch.
Based upon what we had been promised, the charity's cut of the door should have been somewhere around $30.
No one told us there would be math involved...