photoshop to do vehicle wraps? that's crazy talk. why would you want to use a raster-based program to do vector-based work? maybe i'm missing the final step in the process that requires that - like how our production house has to convert/save our AI files to CDR files into HUGE TIFF files (which also boggles my mind, maybe it has to do with the inks and color books, and yadda yadda yadda, but a [roughly] 36x84 TIFF file HAS to be a huge file size) - but that seems stupid to mix programs.
in regards to equipment, depending on what you want to do, if you're just doing regular subs, you can probably get away with small 18" wide mini plotter (a printer with a roll for paper is called a plotter, not a printer; technically speaking, at least in the architecture world), and you can get you a like 16x24 heat press. if you want to do full dye subs, you're going to need a 36" wide plotter to print one whole jersey at a time.
and then you'll need everything/everybody else like steve (and jeff) have mentioned. while i don't do the back end work on full dyes (the cutting/sewing/shipping), i do the front end, and since i'd like to think i know how the entire process works, i think that all sounds about right. correct me if i'm wrong (which has been known to happen from time to time).
but like steve said, research. you've gotta pick a plotter brand, ink brand, material type, figure out where to get said ink and material, whether you want to buy or rent the plotter and who from, then who/where are you going to get it cut/sewn, and then will they ship to the customer for you, or are they going to ship it back to you so they you can ship it out yourself. and in all this, you're going to need to quality check. just because it made it to the production house and they got it all put together and sent to you, it doesn't mean something didn't get ****ed up along the way. THEN you need to start all over again. that 3-6 weeks process now turns into a 6-12 week process.
if you REALLY want to see how it works and what it takes, since you basically live on the top of WI, drive on down to Shirts and Logos (Milwaukee) and see what they do. if you want to see what the production house that the majority of the companies that outsource for their production, head into Canuckland to Mississauga, ON.