Sorry, I only read through a few of the posts, maybe this has been discussed already...

I would recommend you rent the "big" gear first. Things like tents, backpacks and sleeping bags. I don't think you are 100% sold on this activity, plus those three will really help you decide if you want to. If you get a cheap tent, a cold sleeping bag, and an uncomfortable might think that backpacking sucks, when it was just bad equipment that ruined it for you. If you rent, and you don't like it...then you know it isn't the gear, but you. And, you didn't spend a bunch of money on gear you won't use anymore.
REI rents gear.
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