A sole proprietor with no employees is not required to get an EIN. But if you have employees then the EIN is required.
Even without employees it would be a good idea to get and use an EIN. When vendors or clients who pay you are required to issue you a 1099, they need either your SSN or EIN in order to do that. I to am a single owner business with no employees. I have and use an EIN for my business because there's no way on this green earth that I am ever giving my SSN out to a vendor or client. They get my EIN, or we just don't do business.
For those that you pay where you are required to issue a 1099, it's highly advised you have them provide you a completed W-9 form before you pay them anything. That way, come tax filing time if you are required to issue a 1099, you have the information necessary to do so. You can get a blank W-9 form at https://www.irs.gov/pub/irs-pdf/fw9.pdf
