for a $1000, i might consider getting a heat press and outsourcing the printing to a shop that does plastisol transfers. i'd spend some on shirts (keep a minimum inventory) and a web site. i would get a business license (in some states it's free), and hook up with some wholesalers. you need to budget for shipping material, business cards and extras, like stickers, if you want.
better yet, ask this question when you have more money, lol. i'm only being partially flippant, but what people forget is that even if you sell out of the trunk of your car, it costs gas to get there.
if you want to do the work yourself, what you need in large part depends on your designs. screen printing may not be your best option if vinyl will do the trick.