Plus after a year or two, lenders will recognize a portion of your rental income when go to buy the next property.My wife and I began with a duplex that was more or less turnkey, we did a little painting and a little minor foundation work. 

Standing on a 40 foot ladder, in the wind, with my wife holding the base of the ladder, while I scraped and painted.

I'm considering starting an apt. prep business (cleaning, painting, minor repairs) and would like to get your first impression as a property owner and/or manager.

You've painted some broad strokes here.

Insurance will cover mostly new flooring & painting on the walls, but that's about it.  

From the pics, bringing it up to rental condition looks to be largely cosmetic (painting and some drywall ceiling replacement), so COULD be less than $10k.

Anything that appears to be a health or safety hazard on a potential property needs to be repaired BEFORE  it qualifies for financing.2, sellers usually are willing to make/pay for minor repairs such as chipped/peeling paint, cracked windows, exposed wood or things of that nature.

I've been trying to beautify the space, add a bathroom, flooring and paint.  

Perhaps you could offer some labor in return for the privilege of watching the process (demo, painting, landscaping, etc.).

I always paint or white wash depending on the color.