Those are awesome, but they really only scratch the surface when it comes to advanced strategies.

Mold remediation is simple - address the source of water, remove stained and/or wet soft surfaces and treat with bleach.

The house is cigarette tar-laden, so it needs a good cleaning of walls and . . . well, all the surfaces, probably paint, new carpet, and maybe some new bathroom porcelain.

So, we got a quote from him to take it from it's present state to texturing and painting of this 1,500 SF house, interior only, and the bid is $5,620 which is $1.25/SF of surface. 

I'm thinking if I can get both of the properties I would combine them back into one as they are adjacent and re-zone so I could build a MFR quadplex. does this seem like a good idea on the surface?

Has to be on a hard surface, not the grass.  

People can only answer based on their experiences which may be totally different from the actual situation you're in, even if the surface questions (should I get a 7/1 ARM?)

I prefer MS Surface Pro not cheap though.

It was damp down there with some surface mold and random plants growing. 

It sounds like a solid plan on the surface but you are going to have to realize that having tenants right next door might not always be the best thing.