Hi Woody:
My first question is going to be...are you going to be mostly into trout or salmon/steelhead? Most flyfishermen love to fish for trout, as that is really where a lot of the skills in flyfishing have to come into play in order to catch fish...things like accurate casting, matching the hatch, reading the water/structure, etc. Salmon and steelheading is quite different...requiring a lot of patience and finding where the fish are hiding. Patterns used are more like attractors, triggering a territorial or other inate response. Some people who flyfish are almost strictly salmon/steelhead fishermen, that's why I ask.
I don't think that you necessarily have to have your own equipment to take lessons...in fact, as you have noted, it will probably be a great opportunity to find out what rod has the right action that suits your natural casting style the best.
Assuming you will fish for trout a lot in our interior lakes, I would recommend a good medium-fast action rod with a nice progressive taper. A medium fast action rod is a great rod to learn on, and will have the backbone to carry line in the air as you improve your skills, and will also be able to throw any flies that you will want to use for trout and light salmon. Rods like the Sage Launch, GLoomis GL2, Scott A2, and St. Croix Avid are excellent rods to start with, and will have the quality and action that will keep you interested as you get better at casting. Don't get too hung up on the lifetime warranty issue...the action of the rod is more important. A lot of times, the fee charged for S&H for a broken piece to be replaced for a rod with a lifetime warranty costs just as much or even more than the replacement fee forged by manufacturers that don't have the so called lifetime warranty anyway. Heck, even the $69 Dragonfly Expedition casts really nicely, and broken pieces cost something like $15 to be replaced. You will want a 6wt rod. Two or four piece is preferable to odd numbered pieces so they can be broken down quickly into two pieces.
$500 is plenty for a flyfishing outfit. Plan on spending around $250-350 for the rod, $100 on the reel, and $50-200 on a couple of lines (floating and sinking) and backing. Fly reels really just hold the line unless you are fishing really fine tippet (the business end of your leader attached to the fly) or catching really big fish. A disk drag is handy, because if you have the chance to let a good drag system take care of putting pressure on the fish, this is more preferable than using your palm or fingers...which might give inconsistent pressure and cause you to lose the fish. Something that has the ability to be expandable with inexpesive spare spools would be ideal. If you can find a BFR Dragonfly 365 cartridge reel, they are great for the price range.
For a flyline, you can't really beat the SA Mastery Headstart floating line for $38. This has a specialty short head to allow new casters to feel the rod load and unload without having to support a long line in the air. Getting a feel for this is crucial in helping you to develop good line control and timing. For a sinking line, you can go cheaper on this, and there are a number on the market. I would suggest a decent Type II (2-3" per second sinking rate) full sinking line to start with. Make sure both your lines are weight forward (WF) in profile.
Hope that's some info you can start with anyway...cheers.