Dock rental is expensive on the lake. Call around to a couple of the marinas to get a feel for the high end of the market. You will also want to check with the local city ordinances, some out there don’t allow you to rent dock space to non-tenants without special license.
You may also consider that renting the slips to non-tenants could be a major issue if the “partyers” come and go from the lake during odd hours. They may also be “messy”. Minnetonka is a just a big party lake, so beware.