Not everyone who earns a lot of money makes good investments. There are NBA players who made a fortune yet went bankrupt, even ending up on the streets. The first ones that come to my mind are Delonte West and Antoine Walker. They had solid careers, but that doesn't mean they could hold onto the fortune they earned from the NBA. The last time I saw Delonte West, he was in a pretty bad state. So, just as there are good examples, there are also bad ones. Right now, NBA players are signing incredible contracts and many of them don't even live up to those deals. Among them, there will also be players who will go bankrupt in the future due to bad investments.
As far as I know, Walker was able to turn his life around as I see video of him talking on rookies and telling them to really take care of their money while they are young and making a lot. And obviously, he is turning to himself as a example on how not to waste all their money.
But for Delonte West, yeah, could be one of the worst for a NBA player. Videos of him years ago circulating that he is living in the street. The bad thing is that he only has some mental problems and that could really attributed on him declining and life making a U-turn after his NBA career.