Magento ecommerce convertion to order and pay later for website

I have a magento multistore set up with a total of ten websites. All ten websites are configured now as ecommerce with credit card and PayPal checkout options. Currently I need to convert three out of those websites in order and pay later sites. Meaning these three sites are for wholesale only. Therefore merely registered users can place orders and they can place the order as well as pay later using either PayPal or credit card or else transfer or direct deposit. If transfer or deposit is we would want to manually enter the amount deposited or transferred into the bank in order to change the status of an order to pay. We are exposed to the suggestion of the programmer in this point as well. I am seeking a programmer that has already made this type of work thus the programmer will not start from zero. Experience in Magento is a must as well as experience in this particular task is as well a must.

Desired Skills are MySQL Administration, HTML, PHP and Magento