Here's one outfit NOT to book through: tripadvisor.com/…11130209
If you type in "timeshare" + "scam" in the search bar, you'll get a TON of hits (although I'm not sure they'll all be on point).
Bottom line, if you book through something like this, you'll almost certainly have to attend a very, very high pressure sales presentation which will cost you, at the very least, several hours of your precious vacation time. Their sales tactics can be VERY unpleasant so whether or not the cost savings is actually worth it, only you can decide.
The other thing I'd caution you to do is read the fine print very, very, VERY carefully so there's no misunderstanding about exactly what your obligations are, financial or otherwise.
Finally, if you do want to actually purchase a timeshare, do your homework. In particular, research how much units at the resort you're interested in actually sell for on the open market. There are a couple of exceptions but generally speaking, you are WAAAAAAAAAY better off to buy a "used" timeshare than to purchase one from the developer/resort.