I believe the exclusion limit is $250,000 for single individuals and $500,000 for married couples.

I currently have 1 STR and am looking to expand my portfolio into multifamily and single family homes.

Your writing makes it sound like the latter which means they are in fact late every single month and just found a way to avoid late fees.

My name is Malachi.me and my parnters are looing to buy our first investment in Cincinnati. we are looking up for mostly long-term investments using the BRRRR method (Single families)I would love to connect with investors and other people working in the area !

I wouldn't even entertain something like this personally. 

But before that - you might need to check to see if you will be even allowed to do it by your command/orders. 

Their 1 year lease end Oct 31st, even if they are able to keep paying rent, albiet late, should I plan to let them know I wont be renewing their lease at the end of the term?

There's even a group here for people wanting to rent from smaller landlords...verse lux buildings.  

Remember, even with a LLC you still need insurance, otherwise you'll go broke protecting your LLC in legal fees. 

It doesn't sound like you're getting a great rate even with that discount.