My need is pretty simple - start the 3rd page of the document as number 1 - I don't think I need to make the document a book - do I? And, if I do (which I did in order to test) - will it present any issues when I go into production?
In the Pages panel select the page you want to be numbered 1 and either right-click or open the panel flyout menu and choose Numbering and Section Options. Check the box to start a new section and set the start number to 1.
ID will complain about dupliccated numbers when you exit the dialog, so go back to numbering and section options, but this time for the first page in the file, and change the number style to something else (typically small roman numerals for front matter).
I'd create two sections: The first section uses a different numbering style—for example, roman numerals. You do this by selecting page 1 in the Pages panel and choosing Numbering and Section options from the panel menu. Apply a different numbering style as shown below:
After that, you pages will be numbered from pages i - viii if you had eight pages, for example.
Then select the 3rd page, choose Numbering and Section options again. In the dialog, choose Arabic numbering, and start the page on page 3:
After that, the first two pages will be numbered i and ii. The third page will begin on page 3 as you wish.
Page numbers will appear by placing a Page Number marker on the master page. You could use one master page and just delete the page numbers on the first two pages if you like (you'll have to override them by Cmd/Ctrl-Shift-clicking them on the document pages). Or you could create two different masters—one for pages with page numbers and the other for pages that don't have page numbers.