South Shore ski resorts I'm not sure about.
But there are tons of small hotels and side street you can get away with parking for the night.
The casinos on South Shore have large outdoor parking, so that might be OK too.
North Shore casinos are small, so not sure about parking.
Bigger resorts like Northstar or Squaw might (might?) Patrol their parking lot, but small places like Diamond Peak, probably not
My father-inlaw has a condo on North Shore.
Mountain Shadows, 321 Ski Way (looks like a quiet apartment complex).
There is always an extra parking spot in there and no permits or patrols.
You would be a squatter for the night, lol, but I don't think anyone would notice.
90% rental units, so people are always coming & going.