How to add an addendum on current owners management agreement?

[Chris G.]

I was looking to add a new section on current owners management agreements and new agreements regarding an additional charge. I noticed other companies charge the owner a fee like a $100 admin fee or something if we take over a property with a tenant the owner put in place and then have to evict them after a month to two later. I know on resident leases you can add a new addendum on the lease at renewal time but our management agreements don't expire they continue forever essentially unless either party gives a notice to terminate. How would we go about adding this on there in FL? Is it even possible to do or would they have to sign a whole new document?