I am going to buck the trend and give my positive experience of Avon.
I was a rep for 5 years and gave up about 5 years ago when I went back to work full time after taking an extended time out after having my children.
I was one of the most successful reps in my area, making Presidents Club every year. I was a team leader, but very few reps lasted so the vast majority of my earnings came directly from my own sales. If I did it again I wouldn't bother with a team, but just my own sales. I found it easy to find customers in my territory, and from my large network. The products sell themselves, so you don't need to push them.
Now, I was a successful rep, BUT I would only class my earnings as 'good pocket money' - I calculated that I was earning about £10 an hour. I only put in 1-2 hours a day, so it's hardly going to make you rich.
I know the business model has changed recently away from territory, so selling to whoever you like, but I can't see how you are going to make money without some serious legwork. Over half my sales were from my territory, and I had a VERY large area. I would doubt that online sales alone would get you very far.
That said, Avon is a reputable company with good products. I still buy them 5 years on :)
Don't forget you will need to register as self employed and fill out a tax return, which is a bit of a hassle.