As raincoaster said above:
Amazon widget code contains code which is stripped out for security reasons. And Amazon affiliate text links are, in general, banned from WP.com as a violation of the Terms of Service. There are very limited exceptions; when in doubt, ask staff.
If you want a monetized blog and your plans for it mean it will not be among the kind of blogs that are allowed here, then you are in the wrong place. Your best bet is to spend $5 - $7 per month on web hosting and get a free software install from wordpress.ORG.
The differences are clearly explained in a sticky post at the head of this forum and also in support documentation http://support.wordpress.com/com-vs-org/