Think of this and do you want this life. At 12 tonight I leave for Loris SC, 451 miles, with a trailer. Drop when they open tomorrow morning. Nothing to pull back so tomorrow pays nothing. The return load is the money maker.
I would say $1.25 to $1.50 if you really count everything. Then you got to pay you. Like Kenny said empty miles and loading time cut into your money. Making $100 bucks an hour loaded when you are hitting a good lick is great but that’s usually only 1/3 to 1/2 the time if your lucky. So that is really only $35- 50 an hour if your lucky. You will be self employed so taxes, healthcare etc. are your responsibility so that’s not rolling in it.
As for the truck question that really comes down to what you are hauling and what you can afford. IMO money is cheap now so if you have savings hang on to it for operating capital and make payments. You really get to rolling you pay it off early no harm done. If you are really serious and planning to do much long distance go buy brand new if you can. Same for the trailer IMO.