If he’s already messy when he has to clean up his own mess there is a good chance he’ll devolve into a total slop the second he feels like he won’t have to deal with his own consequences anymore.
I’d also recommend some written down outlines and I’d definitely add that deliberate cause messes are not in the scope and also nothing that could be considered harassment or a biohazard.
A surprising number of people that clean private homes have told me their clients would leave used condoms out for them to clean up and so you should make it clear stuff like that is unacceptable beforehand.
If you wash the dirt of the veggies they are technically processed