Jonki said:didnt jacos family help him? and why would he live on the streets?
I don't think Jaco's family was in a position to help him. I don't think they had much money, and treating mental illness back then was far more expensive than it is now (most health insurances did not cover things like inpatient psychiatric care, or medication, try coming up with $20-30 thousand A WEEK for an inpatient treatment program on a session bassist salary, that's about what they cost). If you weren't really wealthy (and Jaco wasn't, despite his fame) you were pretty much S.O.L. back then.
As for being homeless he ended up that way more or less by his own volition. He had apartments and places to live that he would simply stop going back to and instead wander around drinking and snorting coke. Then he'd hit a good spell, try to get things back together, start working again, then everything would fall apart and he'd be back pawning his bass for drug money.
I think the only way I can explain it to those who haven't been close to a severe bipolar illness is to imagine the old Star Trek episode "Mirror Mirror" when the Enterprise goes into the evil alternate universe. Imagine what the evil alternate version of you would be like, now imagine that every few months that evil, alternate you becomes the real you in this universe and does their very best to undo everything the normal you has tried to accomplish when you were in the driver's seat.
That's about the closest analogy I can think of, and that's pretty much what would happen to Jaco during those final years.