The PO Box sounds like a good idea. It will most likely be good as having some kind of mailing address will ensure you look more legitimate.
I`m not a copywriter so I couldn`t give any expert comments on the actual copy, but the general layout of the copy seems to be well done. As I suggested before, for sales pages such as this, remove the navigation so users don`t get distracted and click away from your sales message. Other than that, I think it all looks pretty good.
Did you write the copy or did you hire someone to write it?
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Motivation for Entrepreneurs
Entre-Propel.com