Originally Posted by Amethyst
I would be a little concerned that the residents might get a sympathy vote from a judge, if they plead that "all along, he let us do X, and now all of a sudden he's turned mean and trying to make us do Y."
I live in MD, an extremely tenant-friendly state, and there is definitely a sense that if you have been letting the tenants pay late/pay a little here and there/etc., for quite a while, then you have created a climate of expectation that such liberality will continue. (Sort of like letting those darn kids tromp across your lawn for years, then suddenly accusing them of tresspassing). Granted, the OP seems to be talking about mortgagors, not tenants.
Anyway, just a cautionary thought. I detect the sound of oncoming lawyers, either way.
I don't think there is much risk if
the loan documents provide for late fees. Many legal documents include a clause indicating that waiver of a right does not set precedent for future instances, so if the loan has a similar provision then the OP's past decisions to waive late fees provided for in the loan document should not affect his ability to demand them prospectively.