Is there a grace period between needing to get a business license/ tax ID and conducting business. Want to nail down business activity before paying for anything
Applying for a Tax ID (EIN) is pretty simple and can be done online during the week by visiting: http://www.irs.gov/Businesses/Small-Businesses-&-Self-Employed/Apply-for-an-Employer-Identification-Number-%28EIN%29-Online
Doing so will enable you not to have to use your social security number when you have situations that ask specifically for a business ID, like doing business with other parties or for billing certain entities.
The bigger issues are what kind of "tour" business are you talking about? Not knowing what state you're in, there might be local or state laws regarding the kind of business you're looking to perform that you'll want to be aware of. I read this as "tour" for musicians, but if you're talking about taking people on tours around a certain area, there will be a variety of liabilities that you'll want to ensure you're protected from in the event something happens.
Hope this helps get you started.