She will be transitioning full time into a "real estate professional" for tax purposes.

However, it can legally be used as a bedroom/extra room for the main house.

I have seen on this website answers both ways regarding this (the site administrator saying leave it in Sch A, and his colleague (also a enrolled agent) advising that it can be written off in Sch E, but that there are certain restrictions mainly -- you must have passive activity gains where the deductions are covered (no passive activity loss carry over allowed.

Are you investing mainly for cash flow, appreciation, or long term equity build?

Main issue: if you add an ADU the property becomes a 2 unit bldg., which means it’s under rent control for both units.

Does having a rental property in Utah qualify for a business purpose without needing any evidence?

I can't afford the Boston area, so I've invested in property in Maine. 

The main aspects of real estate that I am interested in would be owning rentals, and working as a RE agent. 

My main goal now is to put together a team for when I really get started investing.

The records or other documentary evidence must support all the following: The amount of each separate expenditure, such as the cost of acquiring the item, maintenance and repair costs, capital improvement costs, lease payments and any other expenses.The amount of each business and investment use (based on an appropriate measure, such as mileage for vehicles and time for other listed property), and the total use of the property for the tax year.The date of the expenditure or use.The business or investment purpose for the expenditure or use