You need a business telephone number and (optionally) a fax number. You can choose to continue to use your personal number as the business number, but that can cause you to get calls in middle of the nights (hello timezones), or sometimes your wife may be speaking to your business contacts. It is advisable to get a business telephone number.
Additionally you may have customers who live in different countries that you. Our business is based in India and most of our clients are in the US.
No body has faxed me in an year so a fax may not be necessary.