I always imagined Mr. Hurst rather older than younger...I don't really have any evidence that he is though! :D
I would agree with you that he must have some sort of fortune...Louisa's character is markedly like her sister's. The fact that she is married doesn't stop her from flirting with Darcy!
Although, if Hurst had high connections in court or something of the sort, it could make up for a lack of fortune (however, considering that his wife seems to outfit herself elegantly, I think it's unlikely that he doesn't have money).