You can have two cable modems at one residence. Sales will argue you can't or will need two coaxial cables but HSI will tell you one coax can handle two cable modems just fine. However, the Comcast computer only allows 1 HSI account along with a cable TV. You'll need to have sales create a 2nd account for your home, usually called an X2 HSI account. So you'll get two bills for your residence. One first TV & the original HSI and a 2nd bill just for the 2nd HSI account. They'll do it, but lower level phone reps won't know how to do it or they'll argue you need 2 coaxial lines into your home when you don't. I had to threaten to get a WISP for a 2nd line before sales would create the 2nd HSI account all by itself. The 1 HSI per account and only 1 account per address is their usual argument but it's not true. Many Comcast markets regularly use the X2 HSI separate account billing while other Comcast markets don't train their reps about it. Nonetheless, I have 2 cable modems using Comcast on 1 coax and it works just fine.
