The unit that is not updated, I've already done significant upgrades like flooring, new trim, doors, appliances and current tenant accepted my increase to $850/MO.

the challenges with flips  is that there are so many angles to try and cover / consider that it is somewhat like spokes on a wheel… even if you just take it system by system… roof, plumbing, AC, foundation, subfloors, electrical, appliances, septic, materials expenses, holding costs, taxes, etc.  

Get those appliances on a Labor Day sale or choose a flooring you want and wait for a price drop while you're working the bathroom.

Maybe throw in the appliances if they pay on time.3.)

It Depends.Potentially capital investments in the properties could have accelerated depreciation benefits (carpet, LVT, trim, appliances), while also allowing you to drive higher rents, thus saving on some taxes in the short run while driving increased values. 

Also, in this metro area, new construction homes from all of the big builders are being sold complete with all appliances and blinds for less than resales. 

(Question 1)My friends expressed concerns about Steve potential retaliation, maybe in ways that I might not be able to directly identify him for (e.g. causing damage to appliances in the common area and I would have no way of knowing who did it.)

A lot of these properties I'm looking at, are mainly just outdated ( Fixtures, cabinets , older appliances ), needs carpet replaced, most have wall paper on the walls , needs an updated paint job both inside in out .So not really things that make it un-liveable , but just mainly need updated Which brings me to ......

If you have four 2-bed/1-bath units with the same appliances, split it four ways and call it a day.

Duplexes have more appliances (2 kitchens and two heating/AC units) so that is a disatvantage but a used appliance can be fixed in an hour, a hole in the wall take a lot more time.