If you have a 3 bed / 2 bath house that is well designed interior, something to offer from a unique standpoint, location acceptable then your going to outperform others who are only doing STR as a "side hustle".

It is always a good idea to do that as soon as possible, since it is easier and typically less expensive to do current appraisals than retrospective ones, where there may not be interior access to the properties.

We overlooked a detached garage (major turnoff for buyers in our price range) and a chimney which required significant exterior and interior work (to the tune of $6000) that was found on inspection.

Adding a bedroom and bath.Along with other interior upgrades: New kitchen, flooring & Paint What was the outcome?

I've completed several condo conversions here in Columbus and the attorney fees were around $5k, plus you need to hire a survey company to provide you with a condo survey, and you will also need to hire an architect to draw up the final layout and measurements of the interior....both of these documents from the surveyor and architect will then become part of your HOA condo docs.

Painting - this can be very expensive and depends a lot on the specific interior.

Maybe a second home could have interior and exterior stairs, plus an ADU.  

I am planning on getting a degree in interior design to help increase my success and potential in house flipping.

One key thing that can't be put into any system is the interior condition - because no one knows it, especially in older markets. 

It was built out without permits, so I demo'd the entire interior and made it an open workspace What was the outcome?