From what I understand there are a couple avenues to repair:New rubber/ metal liner Tearing the box gutters out altogether and extending the eaves to install seamless guttersBypassing the gutters but leaving them in place and attaching seamlessAm I missing something here or is there no economical way to get this done?

As far as drains go, install hair catchers and advise that all plumbing issues that are tenants fault (such as hair, grease etc) are repaired and billed to the tenant.

@Samantha KleinIf the cracks in the slab are only in the floor and not in the thicker portion forming the perimeter foundation, the cost to repair them should be similar to removing an old driveway and installing a new one.

The cost of installation will be dependant on numerous items such as:-how many will be installed, how much jacking needs to take place and at how many points, is it a basement or crawl space, will they be installed on concrete or will post pads have to be dug and poured, is it a one or two story house (how much load will each post have to carry), etc. 

My thoughts were ( and it seems to align with yours) to buy the land, developed it into leasable lots with all utilities and roadways and possibly installed a central pavilion and grass area for the community, then purchase a model manufactured home and up to five for placement.

I want to install 20 or so RV Spaces, 60 or so self-storage units and a drive thru food / coffee stand.

The GFI install corrected a code violation that was also a rehab omission and the charge for that was below the normal charge for an electrician to do the repair.  

However, it is the cheapest option and quickest to install.

We will go to one of my apt buildings and rip out carpet, install laminate, paint or mow a yard.  

It fits in the same wall box as previous models of Cadet wall heaters or easy to install in a bare wall.