My Raptor 700s, and most sport quads, are 4x6. You can get 2 side by side in the back of some toy hauler, if there's nothing on the walls in any way. The RZR I believe is 120 inches long. So if you can get the quads side by side, you need 16 foot long garage. If you can't get them side by side, you are 18 feet long with them both sideways. They also fit in the bed of a pickup nicely. I rode like that wtfh my last toy hauler. 2 quads in my toy hauler and 1 in the bed of the pickup. Worked very well, just watch the weight in the bed with the tongue weight. I never had an issue but it was only a sport quad and a 24 foot toy hauler.
I'd consider a fifth wheel. With the 33 model in the video below (5 feet longer than the one shown in the video) would work well with your application. And your total length is about the same as with that boost. The slide out is nice to allow you to open the door to get out of the RZR. That's a 15 foot long, 72 inch wide Maverick X3 RS going in there.
https://youtu.be/mjGJWWzv5xE