Tax ID

I have a friend that wants to sell vintage clothing online and what I want to know what are the legal steps to making this happen I understand a Tax ID number is necessary, but what are all the steps how would they obtain them.

A tax id is simple just go to the irs website Link hidden: Login to view and fill out the paperwork it is free takes 3 mins.

Is that all that is needed then and then you just keep track and pay taxes and such on what you make?

Thats it