So bottomline is i can have the site, and can sell things i develop on it without a license as long as i report it formtaxes, but if i create a team down the road itd be best to register a business? Also, does it cost anything to register a business in the US?

Paying the correct taxes is definitely very important.

I would suggest you fill out a doing business as certificate with the city/town, county or state government (depends on the state as to which level of government handles doing business as certificates. It costs money to incorporate which means creating/registering a type of business association, (LLC, C-Corp, S-Corp, LP,LLP etc.) I know in Massachusetts the fee to register/incorporate a corporation is $320.00 a year and a LLC is about $520.00 a year.