There are lot of good contractors out there , who work honestly , but the harsh reality is that th percentage is less .

I know that sounds harsh, but they have every right to start enforcing the rules.

A lot of your peers starting out will try and force buying somewhere where it doesn't work, then end up pushed out the game in a harsh manner because of failing to calculate alternative options that will set them up for long-term. 

slumlord is a pretty harsh term, however, let's say-Its a rough neighborhood (some spray paint and busted windows on various bldgs)-A bunch of 2-4plexes on the block-the living conditions of current tenants is bad (partial electricity, no hot water, holes in windows and walls, rats)-some visible mold on a couple walls-doesn't seem to have had any management/maintenance at allOwner hasn't been able to sell for a few years.   

Not to be harsh, but as soon as you started to offer discounts and concessions to them, you were screwed.....they already figured out you are a weak landlord and they can walk all over you....sorry.... you set a bad precedent.Now they may have stopped paying rent and bailed anyway, but with your previous behavior, they smelled blood in the water and knew you were ripe to get bitten even more.Best you can do is start the paperwork for failure to pay, eviction and follow the law....recover the property and move on.Its always a dilemma about  going after the $$ they will owe you....huge hassle and you will never see the $$....but you let them off the hook with no record for the next landlord to find out about.....

Is this too harsh of a reason?

Some advice here may sound a bit harsh, but I think it is just real.

Waiting a month on a promise to pay is costly.Sounds harsh but I learned the hardway.

Due to the harsh winters in my area it was postponed to Spring.

@Vickiana Ramirez I’m not trying to be harsh, just offering my advice.