late fees

[Joe Pitrolo]

How do you enforce late fees? Just send bills in the mail?
I am having a tough time with a few renters who consistently pay late.
I have 12 units and I am thinking about paying a maintenance guy $300 per month to handle all maintenance and pick up some rent of slackers.
I have one girl that has yet to pay this month, won't call back and keeps making excuses- How long should I let it ride before demanding she leave? She is a really sweet younger girl and this is the first time I've had problems although she normally sends the rent late.
I just get tired of being the bad guy, calling people and being ignored.