So are you basically offering a Property Management a-la-carte kind of thing?
I currently have a partnership with someone that does much this same thing. In a nutshell, a handyman and his wife (she was looking to get into the PM space) but when she found out what it actually takes to become an "official" PM (real estate license etc) she decided to do what you're describing... coordinating maintenance calls, delivering notices, filing papers with section 8, lockouts, etc.
I pay them for check-ins, maintenance, delivering notices, meeting contractors for work out of scope of regular maintenance (like roofers for example) delivering paperwork to the Indianapolis Housing Authority for Section 8 tenants, meeting the Section 8 inspector when they inspect the property etc, ect, ect
For move-in/out, I coordinate the rent collection, signing of the lease etc. They show the property and do the move-in/out walk-through. Because they don't collect any money, they aren't considered official property managers so there's no legality issues.
They're moving out of this space and starting another business, so I'm in the market for someone like this, but paying a full on PM is ridiculous for the prices they charge for doing nothing 90%of the time other than being on-call. Also looking into starting this kind of PM a-la-carte in my home city of Denver.
If this is what you're offering, let me know. I'd be very interested and I think many others would be as well.