I'm not sure I'm clear on what you mean? You have 2 sites, one of which you want to get more traffic to, so you want to write articles and put them on both? If that's what you mean, then yes, I'd think you'd have some duplicate content issues.
Agreed. You're going to have some issues if you publish the exact same content on 2 different sites. If you like the topic of the articles that much, rewrite them before posting them. If they're about 50% different, you can avoid duplicate content issues.