ALL of my jobs are in the 500.00 range most pay when finished some pay on friday ,I'm doing one now that is an open ticket 3 complete 4 more to go its a remodel on a foundation working on 3 years in concrete pumping and no bad checks, I was shorted by 150.00 one time but he's on my do not pump list one day I will get even I can wait.

Start taking numbers......credit card numbers at booking, that is.  Pre-authorise it when you take the booking, like a motel does, you're assured to be paid then. 
The 2 or 2 1/2 % is a deal for the piece of mind.  (Money in the bank!!)  Master card rates a frigging ridiculous though, (3 to 5%) so don't take them.  Visa or debit only.  If you want, add the 2% to the invoice, even.  Offer a 2% discount if paid CASH!!!!  But build it into your prices up front!!

Give them either 30 days or a monthly account then when the time is up get on to them, just because the customer is known to be a slow payer doesnt matter- start the ball rolling the moment the account is due- some people in accounts depts. hate being chased and pay to get you off their back. Add a % interest charge to the bottom of the invoice for non/late payment. Get your self a debt collection agency.