I do have them sync their bank accounts and credit cards to eliminate human error in entering items, and ask them to avoid putting personal expenses on those accounts.

You can do this simply by changing your bedding colors and the colors of accent items like throw pillows and towels. 

I develop a high level scope of work and then make my own estimates for each item.

Also the majority of those costs to covnert to a 2nd unit will need to be capitalized and depreciated, but some things (new appliances, flooring, paint, kitchen cabinets) can be shorter year assets vs. across the full 27.5 and IF it turns out that unit is > 50% you can use bonus as well on those items.

Quote from @Ariel Rivas: I don't know your market specifically, but it's typically cheaper to purchase those items at Home Depot or Lowe's.

Only two electrically operated items may be plugged in to any electrical receptacle.

Due to item 1, adding an ADU can require years to start achieving any return (once the accumulated cash flow recovers the initial negative position).4) Adding an ADU is a slow process.

If the credit items reported are up to date with no late payments that is generally good enough for me.

I've read a couple of Brandon Turner's books now and have been getting really into the mindset to start this journey.A couple major items I'm initially thinking of is where to start.

Year 2 had some large expenses, including some CapEx items (water heater, roof).