Interessting, I've never dealt myself nor used anything other than weed. Did you have to look out for gangs or were you affiliated with any gang? During my college days, which was also a looooooong time ago, if you weren't gang affiliated and dealt anywhere close to their territory they, at the very least, put you into the hospital for a good while. 30 years ago was around when Crips and Bloods started branching out, so I would've been scared to death.
I think, and this is only 2nd hand knowledge, that being spotted the drugs only applies in structured, hierachical gang dealings. You get a certain amount of drugs each cycle, you give every cent of the money to the boss of the set and he then gives you some of it back. And as far as I know how much you get back, depends much more on the mood of the boss at that moment than on any prenegotiated amount or how much you actually sold.