The are wilderness and ski areas that prohibit snowmobile rec use. Those areas for the most part are all marked.
I would recommend, Cottonwood/tincup/Hancock/Cumberland pass area. Its far enough away from Denver that it doesn’t get overridden like some of the areas closer to vail.
It’s relatively close to Buena vista and salida. Buena vista has a great cat dealer that keeps most parts that commonly break like bars and break levers in stock as well as ctec oil.
I would recommend to pick up at the minimum a back country radio, beacon, probe and shovel. As well as take a avalanche class. If this coming season is as good as last year expect high avy danger.
I’ll be riding that area all winter if you want someone to ride with.