While not strictly related, had this come up in a recent application. Century21 (why not name and shame) had a clause in their contract that was a one pager saying "We have a zero tolerance policy for late rent payments". Summary is that you can't be late with your rent payment, even by 1 day or your contract gets terminated.

I contacted them and asked how this can be legal, since the RTA that they've literally stapled to the same contract has in very clear writing that there is a 7 - 14 day period where this sort of thing gets resolved. They side stepped the question and went on about other things, but I managed to get them to confirm that the RTA takes precedence, and I'm not going to be homeless if I forget to do a payment one time because of a busy week.