How does car insurance on multiple vehicles work (USA)

there's so many people that own 5+ shitboxes, but there's no way they're paying over a grand a year to insure all of them. is there something where you pay less to add on a car? obviously you can't drive all 5 at once, so is there something where like only one at a time is covered for collisions, and the rest only if like a tree falls on them while parked? asking bc I'd like to be one of those people that own 5+ shitboxes. thanks :)