There are many people who've bought DVC resales through reputable resale brokers, and I've heard of very few problems with the transactions. The only one I can remember is when the resale came through with a lot less points available than had been promised (correct number of point sin the contract, just not as many available to use that year). The broker made up the shortfall so the buyer wasn't out of pocket, I dont know how the broker reclaimed their outlay, but for a seller to promise a certain amount of usable points and then use those points would be fraud.
I know you've said that Vero beach is your prefered destination, are you 100% certain that is going to be your prefered destination for the next 40 years? I would urge a little caution if that is not the case. Vero is a great destination in it's own right, but if you're planning to spend a decent amount of time at WDW, either by first choice or by splitting a vacation I would suggest buying the majority of the points at the destination you're going to spend the most time and the balance at your second choice. You will find it a great deal easier to be able to book all of your vacation using the 11 month window at each resort/destination than having to worry about booking flights and some accommodation a decent amount ahead of time and having to fret about getting the other part of the stay organised nearer the time. If you visit outside of "peak times" this shouldn't be an issue, if your visits are usually at a busy time it could be.