Nothing wrong with having a new truck and the dependability that comes with it. It only takes one day of work to make a truck payment and down time for repairs is usually going to be more then one day, not to mention the cost of repairs themselves.
At least in a new truck you will appear a little more professional. Some MSO's don't care for having their name riding around town on rusted old junker that leaves a big oil stain every place it stops for more then a couple seconds. This business is booming right now and as long as your not a hack and don't mind traveling a little, the next five years are looking pretty good IMO.
Back to the OP's question, with those credit score numbers, you better take any deal you can get and refinance down the road once you can get a score well over 700, I would expect you are going to need at least 10k down payment. Also as mentioned above, there are not any new trucks out there. I recently tried to buy a new van a couldn't get any solid delivery date from the dealers that I was working with. Any down payment is going to be due up front and could be tied up for a year or more.
