Summer or winter, it is crowded with tourists. The town has posted several maps in public areas to assist you. You can ski in Whistler year round, albeit in the summer there is only glacier skiing. The town offers many other summer activities. Mountain bikes are easily rented in the town.
Whistler is expensive.
There is plenty of accomodation, but you will pay for it, especially in high season. Most have pools, but watch for parking surcharges. Whistler is a nighmare to park and many hotels tend to take advantage of it. Its not unusual to find several of these people crowded into a single condo to cut costs. Having said that, there is plenty of work available in Whistler, especially in ski season.