I started by looking at the newspaper on Sunday. I called probably 30 to 40 different companies that advertised before I finally decided on the one I started with. I worked there for 3 years and now they are no longer in business.
It's hard for someone to pick a company for you. If your just looking for OTR then it won't be hard to find at all. I wouldn't think one that accepts pets would be hard to find either.
If your needing training to get your CDL. I would suggest getting it at a local technical school then getting your job. Most of the time you can get your training paid by the state.
21 is early to start. I didn't start until I was 30 and it was still hard to be away from home. Good luck.
Another thing is where you live. Just because the job is OTR that doesn't mean the company hires in every town in every county in every state in the US.
I don't know about accepting folks at 21, but Werner allows pets (with deposit), and has a training program. I know we have some 22 year olds in the fleet, and I got hired at 23.
Give it a shot and keep us posted.