Since the winters are crappy in Michigan, what if you created a total "Winter Protection Package" to "Protect Your Vehicle From the Sand & Salt This Winter!".
Something like: Quick interior detail, apply plastic floor covering to all carpets to protect them from salt/sand (remove it in the spring), exterior clay, quick polish, apply durable sealant to paint (makes snow removal easier), wheel sealant, hydrophobic treatment to all exterior glass, anti-fog treatment to interior glass, install winter wiper blades and fill windshield fluid resevoir with de-icer solution.
I think lots of people would want this done??
Also, you could find a local person that does remote starters and work out a deal with him and make a few bucks on each one. Have every Saturday be "Remote Start Day" and line up a few cars every Saturday. Offer a free basic detail (wash, vacuum, windows) with any remote start install. These are usually very popular around Christmas.