Craig Anderson, from collectables shop Forbidden Planet, reckons Dumbledore figures are the ones to watch.
He said, "They started off at £6.99, but have already risen to £30, because models based on Richard Harris (who played Dumbledore before he died) won't be around for long."
Choose your moment
After you've chosen your toy, and kept it safe, you have to choose the right moment to sell it.
It's best to wait until there is a lot of interest in the type of thing you've got.