Five hundred million bucks? That's a lot of dough to play around with, but I know precisely what I'd go for...
A VW camper van
Yes, that's right, a VeeDub bus I'd then use some 'pocket change' ( ) to seriously modify it I'm talking totally new modern interior, GPS, X Box, sound system, microwave etc. but the fun wouldn't stop there, oh no, I'd then transplant a more powerful engine, something like in a Ford Galaxy, into the rear, and install some 'hood scoops' vertically on the rear side panals (with relevant interior modifications) to act as air intakes to prevent the air-cooled engine from overheating Might have to install a NoS system as well, just to help with overtaking maneuvres I'd top it all off with a custom paint job, and a set of Chip Foose wheels I think that would get me anywhere I'd need to go in a comfortable manner
[Edit to add]
Something a bit like this (but better )