I don’t have a truck driving career (Hell, I can’t even drive a stickshift, for Og’s sake), so I should just keep out of this one, as I know I will be of NO help to you whatsoever.
I wanted to go ahead and post anyway, because my husband does have a truck driving career. He’s OTR and has been for over 20 years.
If you have a family, please consider their feelings. You WILL NOT be around much, unless you can find a decent company that allows you family time, weekends at home, etc. The pay isn’t all that great, unless, like I said above, you find a decent company to work for.
I wouldn’t go to a ‘truck driving school’, but go with an established company that has their own training. You can get your CDL that way, plus your HazMat, if needed.
Starting out, I wouldn’t think you’d be running any ‘real’ HazMat, but, that all depends on the company, I suppose.
You must keep up on all the laws. Federal and state. The DOT (Department Of Transportation) are sticklers for keeping a clean, up-to-date logbook. It is best to go with the DOT rules, as the fines are VERY steep, and most companies don’t pay for YOUR fines or tickets. So, keep that in mind. Most of them want you to run like a raped ape, no matter WHAT the DOT says. You can’t really do that, though. I wouldn’t advise running two (or more) logbooks, because if you do, and the DOT finds them, you’re in deep shit.
It’s a ‘live and learn’ type thing, I guess.
You always have to have access to cash. So, a credit card or two are a must, along with cash. Most companies give you a card, to use for fuel, etc. But, you’ll also need to have access to your own cash, just in case. Whatever you buy with your cash, the company will reimburse you every cent. At least the company my husband works for does.
Food is another thing. My husband always looks forward to coming home on the weekends, to get a decent meal, as he can’t find decent food on the road. It’s mostly fast food or truckstop food. Not the most appetizing stuff in the world, nor is it healthy.
The toughest part is being away from your family for so long. My husband worked for a company once, many years ago, and they kept him out for 6 to 8 weeks at a time.
Now, he works for a great company and gets home every weekend. Truck driver spouses/SO’s are a VERY understanding bunch, let me tell you! 
Good luck to you, Large Marge