Interior is just framing, some plumbing, no electrical.  

electrical upgrades , plumbing,kitchen, roofing, shower, sewer,windows, doors, appliances.. plus I add the first 6month on the loan.My concern is that $18k as leftover in the escrow it should go back to the principal and I only  got  $15K the bank said that the rest is towards mortgage payments… ??? 

I believe, they purchase their houses in better areas (better than ours) and a complete rehab, plumbing, wiring, roofs, walls, fixtures help with longevity.

They also don’t know the little details, like where the wine opener is, and so you as the property owner still have to get involved.and god forbid anything big happened like HVAC or plumbing, they will take 3 days just to get quotes. 

The in-place plumbing will overkill, so if over time you lock and shut down a couple bathrooms (so you have less to maintain), whatever. 

you won't be able to pull a permit. when someone lives in it and it doesn't have HVAC, plumbing, or electrical right and it burns down like another garage I tore down and someone lost their life in linden you'll get hit with a lawsuit. good luck. you'll also be the first person I've ever seen to get a second adu built in linden.

Complete remodel, redid or replaced all flooring, plumbing, electrical, new roof on the garage and retied all the windows.

I look at the electric, plumbing and HVAC and predict when they may be replaced.

For the ongoing/routine items, I'm less sure - though have a pretty good idea of some routine stuff, like lawn mowing, other things feel like a complete guess, like how many plumbing calls will I'll need per year per unit? 

*Periodically inspect all sinks, bathtubs, washing machines, plumbing fixtures, appliances, windows, or anywhere water may be present to ascertain whether or not there is any water present around fixtures.