Most of those large homes, buses and cars are leveraged against the recording studio. The studio's play up the lifestyle and it is a very important part of the culture that watches them. What many do know is in fact many of those younger artists DO NOT own those homes or cars.
The recording studio pays the bills, which is taken from the profits of the artist. Once the artist goes out of favor, its back to the hood. Remember M.C. Hammer? J.J. Cool Jay once made a comment that got me interested in this, indicating he drives a Celica GT and lives in a 2000 SQ FT home, he said basically what I just indicated, the fancy cars, homes and other frills go bye bye when the short career is over.
African American artists really seem to play up this image, it shows that they have broken away from the hood but look we took the "Hood" to Whitey. They show they are no Uncle Tom by perpetuating the Rap Demi-God like stature, however behind the scenes you will find most do not act like that.
In fact, I can use The Beastie Boys as a great example, I forget which punk it was they interviewed but he indicated he didn't let his 3 children listen to rap and that his children attended private school, public school, it seemed by his definition, was riddled with underachievers. Hmmmmm I wonder why genius???