what year cars you work on really makes what system you use and limits it.
i.e. The Snap-On MT2500 is readily available fairly cheaply around the market but is limited to '86-'03 cars with the correct equipment and chips. I saw one on ebay a couple of minutes ago on fleecebay for $500
I guess we'll have to be a jack of all here. Most of my fleet customers vehicles that we'll probably be seeing are the ones out of warranty so I'm guessing about 3+ years old. All of their warranty stuff goes to the dealer(s).