Along the way, I discovered hardwood floors under the tile (unfortunately, not salvageable) and replaced them with new hardwood.

You can only use a handyman for jobs under $500 as I recall....which will exclude tile, drywall, insulation, paint and well pretty much everything.... 

Put drain tiles along the hillside so water doesn’t erode all the way down.

I make sure they're well insulated, have replacement windows, spend more on nice flooring that looks great (plank style / wood-look porcelain tile, hardwood or click-together LVT planks, not peel-and-stick squares). 

Ideally, you know every cabinet placement, tile selection, etc when you meet the contractor for bids.  

Ex: payment upon completion of Sheetrock, payment upon completion of tile, payment upon completion of inspections.

Ours is built with stucco siding, concrete tile roof, tempered windows, self-closing soffit and crawl space vents (they melt when exposed to heat). 

It was built in 2002, and I renovated the entire flooring by removing the original tile and putting Vinyl flooring in, there is no carpet within the house.

The other unit that turned out to be one bedroom is still vacant and now needs significant repairs and I barely see any revenue because of all of the ongoing repairs that are needed (eg the kitchen tile has come apart).

I invested about $4000 in paint, tile, repairs etc to get it ready to be shown.