I’m a DVC member, but only for a couple of years.
Fundamentally, it’s a timeshare. Most of the standard timeshare caveats thus apply.
You probably hear things in their pitches about how you’ll “save” money in the long run. Ignore this, because if you don’t buy in, you probably wouldn’t be spending a week every year at Disneyworld in their more expensive rooms.
Yes, some people “rent” weeks out to others on the open market and make some money for years they don’t go. Don’t bank on being able to do this, however.
A fundamental rule of any vacation is that you should not finance it–if you don’t have the money in the bank to pay for it, don’t take the vacation. I consider DVC, or any timeshare, vacation spending. If I couldn’t have written out a check, I wouldn’t have bought it.
There is a resale market for people trying to get rid of their points. You can get points cheaper that way (though not absurdly cheap, the contracts have a clause that allows Disney to buy the points back if they’re undervalued). But note that since it’s a points system that allows borrowing of future points, you will see a lot of “stripped” offers that you wouldn’t be able to use for a while.
Disboards has a whole section dedicated to DVC, you will get a lot of good information there.
As a single guy, I bought enough points for a studio at Bay Lake during peak time (Christmas). Since I don’t go at peak times, I’ve already accumulated quite a decent surplus. I’m not yet sure if this is a good thing 
Watching the fireworks from the Top of the World Lounge is pretty damn cool.
If you have not officially contacted Disney yet for their official information stuff, feel free to PM me for a referral name if you want. If you have a referral, you’ll get a discount if you choose to buy. I imagine I would get something as well.
That’s what I can think of offhand.