You have a life now that you have designed. 

By asking if you can wholesale it says you want to pass a contract for a fee, if your intentions are something else, you can say so as you really wouldn't be wholesaling if you are simply assisting her (which, IMO, is where your duty should be).You said she had no equity, but worth 90 minus 15 is 75 and her mortgage is 70, that's 5 k in equity, settlement costs will eat that but she has equity.How did you get your rehab costs, what is really needed, I could do a modest kitchen rehab, change out all the flooring, interior paint, and do some outside work for less than 15K.

However I'm unclear how such a change will affect the rentals, especially since I have read that rentals should not be held in an S or C corp (my entity would still be an LLC, with an S-corp tax designation). 

The 50% rule wasn't designed for commercial properties but even their there are crude guidelines as to what works.

When replacing interior doors in a rental property, particularly B/C apartments.

In a B/C apartment that needs interior door slabs replaced.

Matt,Does your $130/sf cost for new construction include soft costs (design, permit, ect)?

Fix soft spots in floors (3/4" osb)  Windows - caulk and plexie glass, Roof - rubber, if exterior is trashed new siding on ferring strips, and white paint interior, carpet (no pad just glue).Make sure 3 things work perfectly: electrical (may need to update), plumbing (pex lines with heat tape wrapped in pipe insulation, and furnace (don't slack on this).These tenants want to move and thins to work. 

So one of the first physical work done on the property was an interior survey and drawing of the as-is building. 

The floor with the two bedrooms is completely outdated (trim, casing, doors from the late 70s) but it very clean and freshly painted.My thoughts are that i HAVE to renovate the bedroom floor: new trim and casing, new interior doors, possibly new carpeting.