When you get to Crested Butte, you’ll be spoilt for choice when it comes to ski/board rental.
You can rent skis/boards in town or up the mountain at a whole variety of shops.
The advantage of renting up the mountain is that they will usually let you store your skis overnight - a great idea, except for the time this winter when they had a gas leak in the main building and no one could get to their gear - ironically for those of us who’d kept our skis at home, the slopes were open and lovely and quiet :-)
If you’re looking for backcountry gear I’d recommend The Alpineer..
Alternatively you can use a very cool set up called Black Tie ski rental who will bring your gear to you. Very civilized.
It really won’t cost you much more, especially if you follow this link to some great discounts.