It helps for warranty claims down the line.For GAF shingles, the 25-year warranty usually requires online registration.

just algebra, or you can plug it in online calculator.If your resulting DSCR is 1.1, not good.

I just subscribed to Pro, but I seem to have 2 different accounts: one for this part of the site and another for the store.

You can probably find an online link about how extreme temperature changes are not the ideal way to heat a home and cost more in the long run.I don't know what the local rental rules are where you are, but look them up and see if you can give her notice. 

Again, the BiggerPockets store has some books on this topic, or you can learn about it by watching podcasts, reading blogs, and interacting on the forum.

Jackie has a good point that much of it is free on line.

And finally, while there are likely some pro accounts that will only give you discounts if you are licensed, most will let anyone sign up, and are often based on volume spent at that store anyways.

I'm not crazy about the big box stores as they seem to charge too much. 

Go to Etsy and search for "rental property tracker," and you will find hundreds of nice spreadsheets to track 10-20 rentals, usually for under $10.Software has extremely helpful features like online payments, marketing syndication (click a button, and your property is advertised on multiple sites), electronic document review/signing, maintenance tracking, and owner reports.

You can research these online.