Skycap has made some good points I'd like to offer more:

1.) Layoffs happen. Mod and Construction would be the most volatile. Service not so much, but you would be very hard pressed to be in service immediately. Probies get laid off first thats anyone who is in their first year in the trade. Then Transient workers, guys from other locals working. Then they lay off apprentices. Then mechanics.

2.) Work is work. Small companies can be just as, if not, busier than the big 4.

3.) Construction is the place for OT. Service and mod? not so much. But I will tell you this: Be prepared to be treated like a dog. If you aren't prepared to be someone's bitch then you might not last long in this trade. You are a moron until you prove to us otherwise.

4.) Atlanta if I'm not mistaken is $42.72 /hour mechanic's scale. Your first 6 months is at 50% scale so $21.36. First year apprentice is 55% 2nd year is 65% (you must complete a year of schooling) 3rd (another year of schooling) 70%; 4th(last year and until you pass the mechanics exam) 80%. However, if you are worth a crap you could be temporarily put out as a mechanic after 1750 hours in the trade and one year of schooling complete. This is the TM position it's full scale. Atlanta is a busy local from my understanding and this can happen there. Then again you might be useless and never get scale but the dreaded 80% paperwork when you have your mechanics card but your company doesn't think you can be a mechanic they'll make you sign it or go to the bench.

5.) Mileage is the IRS rate .58 cents a mile. Its from job to job. Not a daily thing in construction or mod. Your local will have an agreement with the companies in regards to zone pay, per diem, out of town stays and the distances that are required for eligibility.

6.) Do what you are told. Do not be a wise ass. You will have to do most if not all the heavy lifting. Figure out the rhythm of the job. Write Crap down. If you're told 42" it is 42" not 42 and 1/64th" You're going to get yelled at, or worse not. If your mechanic tried to tell you to do better and you tell them that it's just their perspective then well there's not much for you in this trade. Also, don't go bitching to other mechanics about your mechanic it'll come back to bite you in the ass.
Also, leave you phone in your car. if you have an important phone call: tell your mechanic. I have seen a mechanic go off on a guy who was on the phone with his lawyer.

If you have any other questions you can DM me