Buy expensive car. Don't buy insurance. Apply sticky bomb. Kiss $500K good by. I'm assuming this works. I have not bought a car yet so I don't know if they come with some sort of automatic/permanent insurance. If that doesn't work, steal car, pimp out LS customs. Apply sticky bomb. Rinse and repeat until $500K disappears.

This does make all garages completely worthless unless Rockstar lets us own an apartment and a garage later via patch...