Depends on how you're planning to physically fax the items. As has been pointed out, you can use electronic fax services to send an email to someone else's fax machine...although you'll need to use a scanner first to prepare the attachment (or hope that you have a decent enough OCR/scan app for your smartphone to generate a readable attachment on its own).
However, if you want to use a physical fax machine to send the fax, you'll need some sort of landline (copper/POTS or VoIP, as long as it gives you a phone jack & connection via a telephone number).