Thanks again Zach!

Are you saying that in my htaccess I should be forwarding addon.maindomain.com and maindomain.com/addon to addon.com?

OR is it more complicated/involved than that.

I'll def get a developer to do this for me, but I just want to make sure I know what I'm telling them to do and why.

Thank you Zachary. I really appreciate you taking the time to answer this question for me.

Can you (or anyone) please clarify what it means to "edit the virtual hosts on the server directly". I'm not really sure what it means and I don't know how to do it either.

Also, are you suggesting that it's just easier/better to get a complete hosting account for every single domain name?

I find addon domains really confusing. Everyone I've asked so far says that they don't affect SEO but I find that really hard to believe considering the same content is on both a subdomain and a subfolder and also has it's own unique domain. PLUS (in my case) completely different niche sites are sharing the same hosting.

I really don't want to pay for hosting for all of my different sites but at the same time, if it's better/safer to do so for Panda/Penguin reasons I'm happy to do that.

Thank you for your time. I look forward to your opinions/suggestions!