I'm giving you this from first hand experience I'm not trying to scare you off.
You will be hard pressed to find a 2004 and up International with a DT 466 for 13,000 that is not ready for the crusher, major work, or has so many miles on it that they nickel and dime you to death. I would start shopping around $25,000 $30,000 that will put the mileage in the 200,000 250,000 range.
I follow a strict maintenance squeduel at best most trucks will need injectors, and valve adjustment / setup by 200,000 - 250,000 miles also an updateded oil deflector / wire harness assembly a design change as I found out first hand that the older style deflectors are no longer available and nothing aftermarket. Cost? $4,000.00 to the shop depending on how good the maintenance and any other issues. If the truck has a ton of miles on it and the valves have never been touched add in the cost of a head rebuild and possibly lifters and pushrods.
An Allison 2,000 transmission is intact for 300,000 at best 350,000 to R&R the transmission another 4 grand, front axle kingpins bore and sleave $3,000 rear leaf springs $2500-$3,000..... I guess what I'm saying is if you don't want to go broke paying for repairs and loosing face with customers spend the extra money for a decent truck.
Consider this. You pick up a load and you break down or get pulled out of service from a bad D.O.T. inspection. Not only do you pay for the wrecker and the repair, possibly a fine, you don't get paid. Your pay goes to the carrier who makes the delivery. If the bill more than what you're pulling it for you pay the difference as well, and it doesn't matter if its more than you quoted the job at its business. Remember the customer wants their freight delivered they don't care if you broke down.
My non CDL truck started its life off as a rental. Also if you are planning on doing any regional or O.T.R. work that keeps you out overnight you need a sleeper. I know guys that received that ticket and that fine is very expensive.
Good luck
Bob Wolf