Requirements are really state specific.
IL no longer has a FFI - it was nicknamed the "this is a hose, spelled H-O-S-E" class. It was around 80 hours, IIRC, including how to put on your gear, etc. The next step was FFII (national FFI)(240 hours, class and practicals), and the third was FFIII, (Nat'l FFII) which involves a lot more exams, practicals, and theory.
IL also has a statute that allows the [b]A[/b]uthority [b]H[/b]aving [b]J[/b]urisdiction (AKA the Fire Chief) a lot of leeway in determining who is "at an acceptably trained level" for interior FF ops. We have some guys on my VFD who have no paper, but have attended regular, documented training for 15 or 20 years. They're fine inside, but would be insufficiently credentialed in the full-time world.
The work? Fire don't care if you're makin' a million an hour, or doin' it for love, baby. The only difference is (typically) places go to full-time because the call volume overwhelms the part-time nature of a volunteer/call service. It's hot, dirty, wet, choking, gross, sad, funny, whup-yer-ass-when-yer-down-already, and, if you're the type who can handle it, quite possibly one of the most rewarding jobs in the world. Not everybody can disregard thousands of years of evolution and learned muscle memory and go [b]into[/b] a burning building. Firefighters do it anyway.
Depends on the department SOP's. Some have "standby" or "duty" times, usually during typically busy periods (i.e. Fri & Sat nights).
Interview the departments. Ask the Chief for permission to talk to the members (if you can't find the watering holes for the specifice depts., or don't personally know any members).
Aks them what they like about their dept. and job, and what they hate. If they option is open, choose the place where people are the happiest, or, more precisely, where you think you'd be the happiest.
And don't worry - FD's have a high turnover rate - people who decide to do the job eleswhere, or get out of the biz completely. We had a mass exodus to a neighboring FD when a long-time engineer who returned after a hiatus got snubbed on the LT exam.
And remember [soapbox]
there are folks who join the FD for social reasons, those who koin for political reasons, and those who join to fight fires.
Find the "pumpheads". Pick their brains. Listen. Learn your vehicles and equipment.
Knowledge is power, but knowing the ins and outs of this job is a lot more essential than knowing about Mitzi Cunningham's BBQ. It could just save your life (or your rep).