Simple answer: the faster you pay off the debt, the less interest you will pay.

A simple spreadsheet for tracking this can be used, I am happy to share a copy of the one we give our clients. 

As others have mentioned you start on Form 4562, but in my opinion you should have a simple google sheet or excel to track all of this for your properties.

Some come a facet, others don't, just shop around.If you DIY the install you'll save more money.

If booking direct and he has no reviews I would have him sign a simple lease, do a BG check, and have a reasonable deposit.

Turning a single-family into a multi-family is simple.

Will all floors need replacement if I take them all up to work under the house or can a reuse the floors (they are hardwood floor, old and need some refinishing)Of the steps needed, what are the most DIY friendly for a newbie like me?

(to keep things simple)Property was primary residence for Person A from original purchase until 01/2020.

Trying to keep it as simple as possible, but cover the important stuff.  

sub too is a very simple concept and there are just a few items that need to be done to be safe this is not voodoo :)