I spent 10 years in every aspect of holiday ownership / timeshare from the kids on the street with ´winning´ scratchcards all the way up to the reps touring the couples, then sales deck manager.
I have seen every kind of resale / phone room and let me tell you one thing....
IF THEY WANT MONEY UPFRONT FOR A SALE THEN YOU ARE BEING SCAMMED!!
you don´t pay an estate agent upfront fees and the same applies to any holiday ownership.
If you read the so called contract (which will nearly always be faxed or emailed, never recorded delivery) you´ll find hidden in the tiny print that the upfront fee is a listing fee for advertising your details, NOT A GUARANTEE OF SALE.
I was lucky enough to work for the more reputable companies (yes they do exist) but even they had reps and systems that were designed use a ´smoke and mirrors´ technique to show the good bits and not the rest (but that is sales in general to be fair).
Also, check with your resort if they will allow you to transfer it if you do sell it, some even prevent that (mainly actual timeshare)
Hope this helps,
Ryan