You can post links both ways, and is probably a good way to get more traffic and better rankings for your content. However, if you post the same content in two places, with or without a link, your article would be punished by hubpages for being duplicate content.
So, I'd advise against copying and pasting your content in two spots, as it will be punished and perhaps banned from hubpages. If you however write about one subject and can tie that into a post you've already done, that would better you and hubpage users.
As for getting money twice, yes, sort of. Assuming readers will go from Hubpages to your blog. They most likely won't if it's the same content (why would they want to read the same content twice, back to back?).
Hope that answered your questions!