Do you have a closet rod to hang it on? J/K on the spelling of 'hangar' but seriously, be very careful here.
What you will have is an 'improvements' lease on the property. The city allows you to use the dirt as a location for your specific improvement(hangar, in this case). It will come with a lot, a lot, a lot of rules and regs. Get a copy of the lease with the city and I would counsel having a atty look it over. Basically, you have NO rights to do anything but put a plane in, take it out, and store some specific aviation items. Also, in most language the city can modify, or cancel the contract at 30 days notice, and there's not a thing you can do about it, cuz they own the land.
As far as what paperwork should be done, you are going to get a bill of sale from the seller for the improvement, you are going to want to get the agreement from the other 2 parties that obligate you to rent/maint of the hangar, and you are going to notify the city somehow that you are a new lease member. Find the contract with the city, and see what's in there. Since all you are getting is the improvement, you won't get any title, land survey, easement report, etc. I would say that a bill of sale from the seller, and your name added to the lease, and the seller name removed from the lease should do it.
