A:Answer Yes, there's a separate charge for each. At some points in time you've gotten a discount on service for additional units though. That may or may not still be the case, and may or may not apply to the OTA model.
It's worth noting too that for some uses, you migth be able to use a single Tivo, and then a Tivo mini to stream content from that Tivo to another TV, which would eliminate the need for two Tivos, and thus eliminate the second fee-might be applicable in your case.
Also you can buy lifetime service where you just pay once, but I think they've raised the price on it, and I don't think you're allowed to get it on the OTA model. I've got lifetime on both my Series 2 and Series 3 models (the former I've been using for 12 years, the latter for 8, though it JUST started having possible tech issues, so I'm probably replacing it with a Tivo Bolt, or maybe a Roamio OTA).