Long ago, before I joined TUG, I tried to sell my timeshare with an upfront fee company. They did nothing. They didn't even take my calls. I sold it on ebay eventually.
Now if I want to buy or sell, I will use Seth Nock (I know there are a few other reputable brokers TUGgers like as well). I get the best price. He gets (I assume) a good commission. But if I don't buy or sell, he gets nothing.
He emails, he calls. He talks and listens.
Why would I ever pay upfront fee when I can use someone like Seth to sell it for me? Of course I'll pay him a commission. But it will be fair.