Do you have a lot of friends or family that you can sell to on a regular basis? Do they have a lot of friends and family that they would be willing to poke at to buy from you as well?
It's not really an "hours per week" sort of thing, it's just a matter of how many people buy from you. If you sell a lot, you could make good money, if you don't have that many customers, then you won't.
I've known a few people who have tried selling Avon, and none of them ever made much from it. But just depends on who you know, and if you can manage to get a good customer base.