Hmm suppose that could be a neat trick to make lot of money, offer people to do yard work, then fake an injury and sue. Even if you don't win you make good money off the settlement. I guess you have to try to get a feel for the person and use your judgement to make sure they're not that type of person. The joys of the ridiculous liability/lawsuit system.
I'd be more inclined to let younger people do it as they are less likely to sue, and they're just legit picking up money for school or whatever. I'm sure the older man has good intentions too though, but it's just hard to know who to trust these days.