What company offers a thing for wireless internet without having a regular phone/cable or nothing but a laptop?

I will be moving to SF for school in a few months and I need to know how I can get wireless internet for the apartment I'll be living it.

THe person I'm living with has comcast for their tv, but they don't have a regular computer to attach a wireless internet thing to.

How can I get wifi? What companies can I look into?