The guy has a potentially violent, or at least threatening,  history.

Threatening on a monthly basis with legal action sounds awful.

How to Manage paying your contractor:Don’t threaten or intimidate them.

All you "owners" who need the ego boost from telling people that you are the owners will change your tune quickly the first time you are threatened or attacked by some wackjob. 

Quote from @Derrick Ruiz: Guys you are crazee if you think you can strong arm tenants or threaten them in any way and get a way with it.

Just be sure to follow the eviction procedures EXACTLY as they are described on the court website for you jurisdiction: serve the notices exactly as the court requires usually posting them as well as sending a certified letter, don’t deviate from the court website instructions, don’t accept partial payments, don’t do anything stupid like “self-eviction” stuff changing the locks, strong arming, threatening, moving them out when they’re at work etc., and you should be fine.

I am asking because he is threatening to not pay and I need to understand when rent is considered delinquent to issue the "pay or vacate" notice.Please help! 

Don't threaten me with a good time working for peanuts, because I only do what I love.  $$ is really inconsequential in what I do.EDIT:  A lotta you guys remind me of the waiters, waitresses who complain that they aren't paid a minimum wage... but then a law is passed that forces restaurants to pay them a living wage, they FIGHT AGAINST IT!! 

They are gumming up the works and the public utilities move slowly to adapt.Bitcoin mining is threatening the backbone of our awesome hydro power system. 

and a bunch of threatening letters from free legal aid which I just ignore..