4% may be illegal. Consult your attorney, because each state is different. I am 1.5% compound, which I beelive is the maximum allowed by Illinois law.
Collection Notice:
The purchaser agrees to pay 1.5% interest on any payments past due. The purchaser also agrees to be held responsible for any charges that Reliable American, Inc. incurs in any attempt to collect past due payments. These charges include but are not limited to any collection fees by any and all third parties such as lawyers and/or collection agencies, mechanical lien fees, and other legal or court fees. Deposits for special order and non returnable materials will not be refunded but the customer may keep the materials.
The above is a copy and paste taken from my contract.
I like to do the final inspection with the customer as well. It accomplishes two things. 1) I want to find the mistakes now, and sometimes I'll find something minor that needs to be corrected. 2) The customer knows I care, and since during my initial meeting with the customer I explain that we inspect each roof for completion, so I am honoring my promise. 3) In most cases, at least in the residential market, I get paid on the spot. Not always, sometimes people say they have to transfer funds or what ever, and I don't ever make a stink.
The commercial market is different, I often have to wait longer to get paid, but the honest truth is due to Illinpois Lien laws I have to begin the lien process at 60 days regardless if it is commercial or residential. I have only 90 days to file a perfected lien. If at 60 days I give the customer 10 days, then send to my lawyer a few days later he has to give 10 days by law before he files, we're already at 80-85 days.
Some people think 60 days is a little soon to be filing a lien but there you have it.