You'll need to check with your local post office for specialty mailing requirements -- and yes, you will need certificates to mail at discount rates.

Beyond that for your magazine, you'll need editorial, advertising, a good printer and people who will buy it. To get the first advertisers on board, you will need to add tremendous value to your ad space (you may need to give some away at the beginning) and they will need to see a return to keep investing in your publication.

This is the speculative nature of the publishing business, and you may want to also explore something online which can be leveraged in a number of ways and involves far fewer startup costs.

These are just my thoughts -- from someone who has played the publishing game to varying degrees of success and headaches!