What's wrong with the sentence as it stands? The student who built Oculus Rift and sold it Facebook is now wealthy. The professor who had the original idea is not now wealthy; this is in contrast to the student, who is.
It's an unusual construction, but I think it's valid. To say "now not wealthy" would imply that he was wealthy before, which is not the case. To say "now wealthy" would imply that he is currently wealthy, which is also not the case.
edit: look at this square, deleting his comments. He was sassing the author about the phrase "not now wealthy", wondering if it was supposed to be "now not wealthy", or "now wealthy".
