I purchased my Fender Mustang V Head and 4x12 Cabinet from AMS. Basically what it is is a "pay while you play" layaway plan. I paid $100/mo for 6 months. You fill out the info (debit/credit, address, etc.) and they take out the first payment immediately. They will call you before they take out the first payment to make sure you are who you say you are and to validate the account, etc. Once that is done and the payment comes out of your account, they ship the gear to you. I ordered my gear and two days later it was delivered to my job (didn't want it sitting on my porch all day). Keep in mind though that the day you make the first payment is the day they will take it out of that account every month. There is no interest charged for the purchase. Also, if you have an item that does not have a payment plan attached to it (i.e. strap, picks, whatever) they will add the cost to the arrangement for the guitar. do this will make the payment higher because it will be divided up into the monthly plan. If you're worried about credit, I don't think it plays a factor into this type of purchase agreement.
Hope this helps!!!