HEY, Welcome. I think you will find a GREAT amount of info here. dont forget to do a search be4 posting.
you having been in the business for a while. about the only advice I can give is, decide on what type of company you want to have. " As in-work for anyone, or high scale customers "
I can speak from advice. get your self an agreement. for the customer to sgin. give them 10 days to have there payment in your office after reciving the invoice. mail out on the last day of the month and have it due on the 10th. if not then charge 3% interest, anythign after the 15 RE-INVOICE them at a charge of 35.00 after the 20th. STOP SERVICE.........
I know this sounds harsh. BUT do it right from the get go and there wil be NO issues.......
Best of luck to you