"Is SFI good for students (18 or older)? Why or why not?"
I would say yes it is an excellent opportunity for students.They often have a very limited budget and SFI offers them the chance for little or no cost to boost their finances.The hours that they need to spend on building their business is also very flexible so would fit in perfectly around their studies and there is also the chance to make friends and maybe share ideas that will help both in SFI and everyday life