All those questions have different answers depending on individual situations. New or used? Good things about new- Warranty, original owner, can somewhat spec out what you want. Bad things about new- Price, price, price oh yeah and truck payment. If you can afford a new truck or if you are running team and are aware of what kind of profit you require monthly, than go for it. If this is something new or somewhat new for you, try a more modestly priced used vehicle.
Next question, medium duty or heavy duty? Pro's on heavy- Last longer, handle heavy weight much better, longer warranties, etc. etc.
Cons- fuel efficiency. Normally medium duty's get 10-12 mpg and heavy duty's get 6-8 mpg. If you looking new, a class 8 will cost you more especially when you stretch it and add a box, but it will last you twice as long. If you are looking used, class 8's are usually affordable.
2 or 3 axle? If you do class 8, use a tandem. Class 7 probably stick with single axle.
22'-24' is usually the best size box for straight trucks.
Good Luck,
Abc
