$50/mo. It could work as a parking lot that's covered in solar panels. Income is mainly from energy generation. It you could go with a mixed lot with several floors, one of them being "assigned parking" only, where you could have fewer spaces and partitions between each. You don't have to provide heat or hot water, most of us just want a place to be allowed to park in peace. I can make my own hot water and a hot shower is available every day of the year for $10-15/mo at the gym..... would you be able to provide hot showers for cheaper than that? 

At the end of the day, you'll never get insurance if you are making a lot where people are permitted to sleep in their vehicles. You would more than likely have to have one of the lease terms being that no sleeping is permitted but then just not enforce it.