I'm a registered nurse living in the United States and working under a
TN work visa. I would like to open an internet business but am unsure
as to whether I can or not. If you answer please provide possible
options and links to sources of information.

hi.  I'm also Canadian on a Tn and my understanding is that TN Visa is
specific to your employer so you could not use your visa to work for
someone else, even yourself, if you incorporated your Internet
business.

However, if you're just going to start an Ebay business on the side to
supplement your income, I would think it would be no problem to just
do it.

Alternatively, if you are going to start a "real" business, with
employees and real incoporation, you could create a partnership with
someone else and have them hire you as a consultant and get another TN
visa.

Hope this helps