I invoice after every job. On the 25th of each month I sent a monthly statement stating each customer's balance. They have 15 days to pay, with a 3 day grace period, after the statement is sent, or late fees incur. Most send payment when they recieve it, others pay me right after the job. If a customer gets behind more than two months, after calls and letters, I drop them, trying to weed out the non/slow payers, I had enough of it last year.
I love my system. I just developed it last year. Used to, I would just get paid per cut, or if they werent home, the next time i cut it. and sometimes i would forget to invoice, and i was all out of whack, and sometimes i would lose track of my accounts and their balances. I am much more organized this way, and havent lost track of any balance yet.
My set up:
-2007 Chevy 2500hd 8.1l 4x4
-7x18 enclosed trailer
-Grasshopper front mount 61", gravely 52"
-36" Gravely Walkbehind, 21" exmark push mower