Most of the affiliate managers will try to work with you if you let them know how and where you expect to get your traffic from. It'll also depend on what your site subject matter is in relation to what you're wanting to promote.
I've been denied a few times when joining an affiliate network because I didn't have a site up yet for that particular niche. Once I explained that I wanted to start a new site but had to know what I would be able to promote first BEFORE I made the site.
Then I was ok & approved. So try to talk with an affiliate manager and keep them "in the loop". After all, they want YOU to make money so they can too!