I dont know of anyone living on the streets. But MC hammer had to file bankruptcy. I think people said that he was living in a car, but i think that was a rumor.
The woman who played Lois Lane in the Superman movies with Christopher Reeves went crazy and was found living in an undergrowth in LA. Margot Kidder her name is. She suffers with Bi-Polar. Gary Coleman was a celebrity but last anyone seen of him he was working as a security guard somewhere.
Bobby Brown. Supposedly he blew all his own money, then hooked up with Whitney and they blew through much of hers. After they split, he lived out of his car (according to him) before he started down the reality show path. Quite a downfall for someone with the huge ego he once had.