Nice, so you structure the CoC with that 5 year window. 

id=1IaAr5B1WeT...Cleanup Job (Low cost fast flip): landscape package in front remove deckremove vines from house clean exterior, fix siding and wood rot, paint neutral beige/gray color clean driveway/weed, clean retaining wall/pavement replace flooring with mid grade flooring bottom level, carpet upstairs replace interior fixtures paint interior white trim, light color beige/gray walls, popcorn ceiling removal new kitchen appliancesRehab options: Replace deck with new one (kind of awkward that high to me) vs Remove and fill in wall or add large window to master.Potential space to move laundry into upstairs bathroom closet vs basement Can maybe get away with toilet/vanity replacement in each bathroomUncertain if painting or replacing cabinets with ikea type is worth itAny in-ceiling lighting will open up codes stuff with electrical since it is out of dateRepave/fix concrete front porch and side porch - replace/paint railingReplace front walkway cement, or remove walkway and replace with right angled walk to driveway (may not provide ROI)Tear down vs paint garage port in back yardWhich do you think provides highest ROI? 

I am talking about store fronts with bullet holes in the front windows.

I mean, the replacement cost of a window, or painting a room has little to do with how much rent I expect to get from the property.

Too true @Gary Ennis, we have wedding pictures showing neighbors leaning out of their 2nd story windows to watch our wedding!!! 

Sure, your MU-2 zone will allow zero setback, but you will not be able to put any windows or opening in walls set on the property line (assuming its not a corner lot). 

When your investments go on the skids, they will slide away too!

Personally, if no windows, electrical, plumbing or structural work is being done I would just get it done.....typically no permits are required for that but theusually are supposed to have “some kind” of license...here in PB county it’s not just the regulated contractors (gc’s, plumbing, electrical, ac, etc) but guys just doing painting, Sheetrock, etc. .....not that it happens all the time of course.

After buying the property and viewing it I quickly realized why noone had rented either of the vacant units: both units had what looked to be mouse crap on the floor and the other unit had a broken window (not cracked - a literal hole in the glass) and there was a hole punched in the drywall (covered using cardboard). 

How old is the home- are you incorporating longer term rehabs- like roof, plumbing, windows, electrical and Heating/ & AC?