Saw this post this morning by Janet Reid about the weird ideas muggles have about how authoring works.
The scenario is both funny and familiar to me, though I haven't had to deal with it in a while. I'm grateful for all the years I went to writer's groups and small local cons and especially being a vendor/cosplayer at Planet Comicon because they gave me ample opportunity to build a catalog of awkward-diffusing phrases and responses.
Awkward sitch #1: Someone wants you to write their idea and you split the profits.
Response: Oh, thanks, but I don't do collaborations. I like to have complete control of a project.
Awkward sitch #2: A beginning writer wants you to critique their manuscript.
Resp: Sure, I charge $80/hour for professional editing services. (These days I just say I don't have time, which was true. I do, of course, have an established writer's group and we reciprocate reading/editing favors.)
Awkward sitch #3: A friend of a friend asks you to edit their raw wound of a manuscript that they wrote during therapy and offers to pay you ridiculous amounts of money to make it sellable.
**WARNING: No good can come of this. Do not succumb to temptation.**
Resp: I'm flattered, but I simply don't have time. You want to find a professional editor who can do it justice.