[froztbyte]

(all below is in an American/US context)

Read about ILECs/CLECs. Understand what the cable offerings' contention model is.

Do the math.

Understand the support burdens of NAT-on-NAT.

Run the numbers of RF contention, and shared-medium bandwidth management.

Do the math.

Probably the best advice I could give here: It's very easy to do a mediocre job of all this. It's a fair bit harder to do a good job of it. And think of how much you dislike the mediocre ISPs.