Had agreement to hire me, then they backed out last minute - System Administrator Jacks Small Engines & Generator Service Employee Review

I was supposed to be starting in an IT position with this business. Completed two interviews. I was told they had chosen me, and we had agreed on a salary and a start date. They just required a Drug Screen and Background check. I went and took the Drug Test and filled out the Background Check. Few days later we were still awaiting completion of the background check, and I get a call. They rescinded the offer. I was told "someone from an MSP (Managed Service Provider - for any non-IT people) that already assists their IT Dept decided to come on board, so since they already know the place..." Extremely unprofessional. Prior to receiving the call, I was going to put my notice in at my current employer VERY soon to line up with the start date. Thankfully I hadn't, or I'd be jobless AND homeless. They don't care that their potential candidates have to arrange time off of their current job to accommodate interviews. They don't care that you have to do the same to complete a drug test (or use what little free time working adults have). They don't care that they'll ask you to do all of that to your CURRENT employer, under the premise that you'll soon be leaving anyway, then suddenly at the last moment change their mind. Be wary of this business.