Looking for advice on how to charge late fees.

[Audrey Thomson]

This is my first rental property (townhome - 3 units) and I am drafting rental agreements. For those of you with experience, what would be your recommendation on structuring late fees?  Should I do one flat fee? Or charge a daily fee? (In Texas there is a two day grace period after the rent is due, so if I charge rent on the 1st, I can start charging late fees on the 4th)