Which gym are you going to attend- I live in Phoenix and spend way too much time lirking about in gyms, worked at a couple. It has been my experience that, in these types of set-ups, the focus will be on the aerobic, "conditioning" aspect of the workout. I don't know how exactly the routine would differ for a more serious boxer; the place I worked at tried to discourage such things and, damn it I know I look like I'm trying to kill a snake when I jump rope.! Seriously, I would suggest stdying and practicing punching technique on your own; this is woefully neglected at all levels of boxing. Also, footwork; don't get in the habit of getting your wieght shifting when you jab as it makes every subsequent punch a three step process. Plus, you can't move. (try it; from a boxing stance get your weight up front and try to move.) Work on defense as you will be taught a variety of silly things like slipping without moving your feet; works great unless you'd like to punch back. Finally, starting late is what it is but at 30 you aren't old. Too old, probably, to be thinking top ten pro, but not too late to acquire some degree of skill. Master the basics and add new things selectively and learn them well. Oh ...after you get started remind me and I may be able to help you with my counter punching made easy theory. Best of luck