My dad is in the suburbs of Indianapolis. He's got Comcast. He realized this week he's been paying -- maybe for years -- for hardware he doesn't actually have. And he's renting their cable modem. He's getting refunds, scrubbing service costs, and while he's at it, wants to buy a cable modem to cut that rental fee. I've got FIOS. I've never had a cable-modem rental fee and don't know anything about buying one. What should he buy?