Typically an ADU is inferior in size to the main improvements.

Let your lawyer add in penalty clauses for inferior work and non compliance with the time schedule.

They use under gauged wire, 2x2 walls, and inferior building supplies.

I suspect those players are going to keep the best notes for their fund as is their fiduciary responsibility to the fund and their clients.. and then off load the ones they deem inferior for what ever reason to those like you

Things that can be issues; superior liens like IRS liens, Inferior liens or judgment holders who were not notified, or even the quality of the title the previous owner had.

Your case is better than the average investor, because others are claiming inferior or incomplete rehab.

Also - if you are a first time home buyer, make sure the lender will answer your seemingly naive questions without making you feel inferior. 

A house across the street to it that was inferior to it when they were both built (cheaper) sold two years ago for $385k in like a week or two market time. 

You and your boyfriend might be tempted save money doing the renovations yourself, but if you're paying someone else for labor and materials than you'll be more worried about quality work than doing an inferior rehab.

You have a product that's inferior to other listings.