The issue is it will be short term so what are you gonna do to pay it off.

:) To follow up on our conversation, each DSCR will have different requirements however I am not seeing an issue with you not having personal rental history so you should be good there.

I also bought quite a few 20 40 80 acre tracts and would bust them up as well.. it was pretty cool because in Oregon logging permits are a snap.. you dont need any county grading permits to bust in your logging roads so say I had a 20 acre that I was going to short plat into 4 5s we would put the road in the logical spot for each parcel future access and then put a few landings in the logical spot for the homesites all under logging permits saved THOUSANDS .. then sell off the lots..

My lease says the rental will be provided pest-free and I will cover any pest issues for the first two weeks.

Some insurance companies have told me they don't insure LNC buildings cause 'replacement' wouldn't be a straightforward process, as there's usually no detailed record of such grandfathered buildings' layouts in the records to permit re-building following a fire, flood, quake, etc.Others have said at least in while securing quotes, it's a non-issue.Surely they both can't be correct!?

It sounds like the passivity of having a new construction rental with low cap ex and hopefully not many repairs would be beneficial in your situation.I am not sure which exact community you are considering but I would definitely make sure whatever builder you are going with is high quality to avoid long term issues. 

It won’t technically be an ADU as I can permit a full second dwelling, but it will be similar to a large guest house. 

Do you think I'd have issues renting it out and/or selling it?

Zoning, permits, etc. 

You'll operate without issue in Phoenix.