You are now on a month to month tenancy. If in your previous contract a late fee was imposed for late payments then that would transfer over by virtue of you still being in this place and therefor any lat rent now and in the future would be subject to any late fees. Under a month to month tenancy where there is no lease either party can cancel the tenancy with a 30 day written notice to the other party. If the owners decide at some point to cancel your tenancy you will still owe any rent due for that last month.
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