I would say to expect a floor rate of 6-6.50%

Sixteen homes to inspect- roofs, hot water tanks, soft floors, siding damage, decks, porches, furnaces. 

You are better off finding a solid property that needs light cosmetic work (paint, floors, or maybe even a kitchen or bathroom remodel), buy it at a decent discount and put 25% down or more (this is when you get best rate terms). 

I believe I can do this with the upstairs rented out at $1,650 a month and $1,750 for the main floor unit. 3bed 2bath down and 3bed 1bath up.

But one of them had about 150 callers on their floor of their office and the other had about 600 employees..

For rentals, would a single floor or two floors makes sense? 

This is the roof of the first floor. 

So take a floor for yourself and add a kitchen. 

The limit on scaling is your deal flow (mine never was that good) and time it takes to perform the value add (I got fairly quick for example, my last rehab did all new plumbing, electrical, and flooring.  

Real estate investing has a floor... the land+.