The first and foremost DO's to being an awesome sponsor is: "always lead by example"
We can say that it means to show an evidence to what you want your PSAs to do,
So in my opinion the best way to convince someone that, they can earn a substantial income in SFI, is to show them your earning from SFI.
This works for some affiliates who earn substantial income, for those who do not, they should convince themselves first.