I discovered a new phrase yesterday (tax years) and I am not sure if I am smarter or more confused.  

There is a TON of information to discover with REI, so try to focus on the stuff that really applies to you or that interests you. 

They were scheduled to close escrow in a couple days only to discover the seller has a lien on the property for a debt that should've been removed in their bankruptcy 5 years ago.

OMG, am i about to discover kegs of wine is actually a thing? 

Heck I barely read the BP Blogs anymore.

Here's an article to help you further.https://www.biggerpockets.com/blog/how-to-find-off-market-multifamily-deals

My insurer requires my tenants have their own insurance.This happened three more times before the actual reason was discovered.

Here're some articles to guide you in the right direction: https://www.biggerpockets.com/member-blogs/10850/84064-what-type-of-investor-to-be-when-i-grow-up-active-or-passivhttps://www.biggerpockets.com/member-blogs/10850/85836-should-i-buy-a-turn-key-property-or-invest-in-a-syndication

You're going to discover a lot more damage inside, a lot more cleaning than you expected, he won't repair the latest broken window or the three before that, and he probably won't even be out by the scheduled moving date.

BP Podcast Episode 138 has some good info about self-storage. https://www.biggerpockets.com/blog/2015-09-03-bp-podcast-138storagesystemsseo-michael-rogers