First let me point out that you are looking to buy from a current owner. If your mind is made up and you want to buy regardless of how much advice you get not to, then that is far cheaper than buying from the resort.
Now some advice: DON'T BUY TIMESHARE ON SXM UNTIL THEY PUT IN SOME LAWS TO PROTECT THE BUYER. (I will point out the obvious exception - the seller is dumping at a dirt cheap price)
Resorts go bankrupt, are sold at auction and the new owner sends you a notice that you no longer own your weeks. We have had that happen twice.

Bob