Normally, you get paid a $750 advance at the beginning of the month. The rest of that month's pay is paid the middle of the following month.
For example, on January 1 you get $750. On February 16, you get paid for all of January, minus the $750 you were paid six weeks before.
For training, I think you get your advance check the first week, then they catch up on the regular pay sequence on the next check. But I could be wrong.
Unless it's changed, trainees stay at the LaQuinta, so charging meals to your room would be a little hard. The places to eat close to the LQ suck, but there are a couple places across JFK Boulevard. Somebody's bound to have their car though, so that'll help break the monotony.
If they have you staying at the Marriott, there's an underground train (and pedestrian tunnel) that connects to the terminals so you can get your grub on. You'll get your CAL ID on day 2 or 3 of class, so you'll be able to get through security, and get the standard 10% airport employee discount. And IAH has some pretty good places to eat, especially Terminal E.