I have a student that trades barn work and babysitting for lessons. Her parents pay for 1 lesson a week but she wanted to ride more so I am allowing her to work them off. It's great for both of us!
That being said, it's a family that I've been working with for many years, this is their 4th child that I've taught to ride (2 currently) and I also have one of their horses in my barn for training w/ another coming tomorrow. I'd be more leery about doing something like that with someone I didn't have as much history with.
Life is like a camera. Focus on what's important, Capture the good times, Develop from the negatives and if things don't work out, Take another shot.