Inspector also noted window screen was broken and needs to be replaced, paint on kitchen cabinets was chipped and needs repainting, paint on multiple walls was chipped and needs repainting, and the garbage disposal was not in working order and needs to be fixed.

People are more likely to dig into something and estimate costs for you (to get your some data points) when you have a specific situation/project and possible solution proposed.Other advice would be to see places and get used to walking around the Menards/Lowes/Home Depots of the world to more quickly be able to reference standard stuff like lumber, finish materials, windows, etc... 

One was a just a broken window pane.

The living room downstairs has no windows with vinyl floor and a large carpet mat in middle. 

Added a 18' X 26' addition on the back side, new windows, siding, doors , roof.

If you intend to use it on things like restoring the original windows, your best savings will come from finding the right person to do the job.

If I weren't paying $400 to my HOA every month, I theoretically would be saving that amount to: replace my own roof and windows, maintain the exterior of my home (painting, siding, porch steps, etc), pay for my own landscaping and property security, etc.

Floor heaters and window units.

For example, the stall would have an oversized single garage door, and the depth of approx 1.5 full sized trucks, with room for a workbench, perhaps motorcycle, windows, etc.Question 1: What advice might you offer for building design options for this new 7 unit rental? 

I have looked at this property and it's in really good condition the only thing it needs updated is one of the units currently has window AC  but i can update the central so i allocated some money for one for 3000.00.