What it's worth?
I often wonder what my Biz could sell for in a few years, also just the idea of what it is as a asset even though it has no weight as collateral (it would just be nice to have an idea).
But like you, I don't do contracts. Mainly because I feel it is good for either party to be bound to a service contract would be detrimental to both parties. If they couldn't afford my services any longer than so be it. Just pay me for what I'm owed and we are good. If I start working for a PITA customer and they force my hand I don't want some contract binding me to stay working for them. (I am sure everyone has had a few of those huh).
I would think though as long as you were selling to a reputable person or company that the client list would be worth something to them. As long as the term, no compete clause was included.