I developed a mini online numbers betting system based on paypal payments. Would it be a profitable business?
Yea, sounds like you better talk to a lawyer about online gambling. Im sure their are rules, regulations and licenses you need to aquire. I would start with Paypal's TOS agreement like Dollar said, then make your way up to the other aspects if you want to keep it legal and long term.
Paypal will lock all related accounts so friggin fast if you do that. That's exactly why all these type of schemes use egold, liberty reserve, or some other form of sketchy payment like that.
It's way risky and you'll probably end up getting your PayPal account banned for it. I wouldn't recommend it.