Considering AIT, they say that I won't even start training unless there is a job with one of the carriers. Once I start with one of these carriers, what kind of stretches away from home can I expect?

I have to defer to someone more recent at this than I. In 2005 it was only a week b4 my husband got assigned- diff carrier tho. He flew out 11/5 and I didn't see him again until 1/12. And he fought hard for that. I wish ya luck- it's not all bad- you get home sometimes. It's just gonna be rough out of the starting gate.

That all depends on what division of the company it is. I've been with Werner for over 2 years and I get home weekly. Then again, I'm on a dedicated account (DG, South Boston, VA). Some dedicated accounts like Dollar General (which both Werner and Swift have, in various areas) and Family Dollar will get you home weekly, but some will keep you out for two weeks (like the Werner 'surge fleet,' or Perdue chicken), which is about the same as if you run regional. If you run 48-state, expect to be out for 4 weeks at a time. I don't know what it is for Swift, but I don't imagine it'd be much different. Call driver placement and ask what's available in your area...
Wait, where DO you live?
Also, what do you want to do? irregular route van? flatbed? reefer? dedicated?