I think any time's a good time to at least try, cuz you don't know if it'll work if you don't! I'd personally go with crowdfunding, though. That'll give you a better idea on whether people will buy them and you won't be out however much it costs to get them printed only to have a couple people buy 'em.
I've also seen a lot of other folks kickstart with just a first chapter and succeed, so I think just a chapter is fine.