I don't think you are clear on this so I will post a summary. Do understand that purchasing a domain name and domain mapping upgrade changes nothing.If the blog remains on free hosting here at WordPress.com it is subject to the ToS.
Before Upgrading – Important Notes
Same Rules Apply – The Domain Mapping Upgrade does not enable the permission to use advertising, any kind of prohibited code, or upload additional themes or plugins. With the upgrade, your blog will still be hosted here at WordPress.com, which means that you will not have FTP access to your files and you will still be required to abide by our Terms of Service.
jusjennifer already posted the relevant links but I'm not convinced you actually read the entries.
In a nutshell no blogger initiated advertising, retailing or reselling the work created or services provided by anyone other than yourself is allowed on free hosted wordpress.COM blogs. E-commerce transactions via shopping carts and the like cannot be conducted on free blogs from and being free hosted by wordpress.COM
The advertising exceptions noted in support documentation are for high traffic blogs that qualify for and are accepted into the Ad Control program, and for extremely high traffic blogs that qualify and are accepted into the paid VIP hosting program.
The exceptions noted in support documentation with regard to affiliate links are found here:
Affiliate marketing blogs: Blogs with the primary purpose of driving traffic to affiliate programs and get-rich-quick schemes (“Make six figures from home!!”, “20 easy steps to top profits!!”, etc). This includes multi-level marketing (MLM) blogs and pyramid schemes. To be clear, people writing their own original book, movie or game reviews and linking them to Amazon, or people linking to their own products on Etsy do NOT fall into this category. http://en.wordpress.com/types-of-blogs/
If you have any further questions about advertising and/or affiliate links and/or ecommerce on a free blog from and being free hosted by wordpress.COM please contact Staff directly using this link. http://en.support.wordpress.com/contact/
If you do require an ecommerce site, advertising and/or affiliate links you can hire a web host and get a free software install from http://wordpress.org Refer to > http://support.wordpress.com/com-vs-org/