Since I shall think as an investor, I cancel all my ADU build project and swap them with a duplex.

@Simcha Davidman, You did a drop and swap. 

Swap out the water heater especially if it's the original.  

However, if the heat is electric it is far easier to add an outlet for the stove and swap out the water heater to electric so everything is electric and you can cut out an entire utility...  

A good drywall repairman is a valuable member of the turn team.Also there is a prime-ing and painting to do, swapping out brass fixtures for silver colored ones, and a biggie--door replacements for kicked interior doors.Changing front door locks, changing interior door handles, knowing how to true up the locks to the lock plates so they work like hot butter.Knowing how to repair a broken screen, knowing how to change water hoses on a washing machine, every year.Being able to give a front door a smooth paint job with no brush streaks, steel, wood, fiberglass and antique doors with varnish on them.If you and your customer both have an iphone you can use facetime (free video chat) to connect real time, and the customer can see what you see as well as hear you.

You can swap 6% with 5%.

Make an addendum swapping out one tenant for the other in Docusign for all to sign?

Second - you'll need a septic....homebuilt w/55 gal drums is perfectly fine, but won't pass a real inspection.Third - You need a propane tank for cooking, heating water, etc.... just haul in 100 gal tanks and swap the out yourself....or get a 300 gal tank from a company and have them fill it every 3 mos.Fourth - A couple solar panels and a few batteries for lights and charging like you saidThis is not cheap nor is it easy, but it is fun.

The ordinary homeowner is not capable of actually performing maintenance like swapping out a motor.Pay for it this time.

All of our grills are plumbed to natural gas, so no tanks to swap.