I've worked on a few sets, mostly in grips. Last set I worked on, the sound mixer needed a boom guy, and I volunteered. Had a blast doing sound. He let me mix by the third day.
Anyway.. I've been asked by the director to come back, and I possibly have other jobs on sound too, as I've been bit by the sound bug.. So, I'm thinking of buying some sound equipment, and I need some opinions.
Research and price wireless lav rentals in your market, and always ask the UPM (or whomever is hiring) if you're going to need them for the job. Lectrosonics UHF is the standard. You could easily drop another $4k on a pair of wireless, renting would be a great way to start out.
Don't forget to get some rental compensation for your equipment. If you do it now you'll be better positioned to get more $ as your equipment inventory increases.