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I guess for the home-page go for the highest searched first; but due to the fact that you would want to rank for "Ski Rental" and "Snowboard Rental" I would also consider doing two separate pages in the website which tackle each separately; this way you would have a page optimized for Ski and another for Snowboard with more details on each. This way you could still capitalize on both. For the homepage I would probably go for  "Ski & Snowboard Rental Lake Tahoe"