You don't even need a sub-account to have two ISYs, both of mine are just on the one portal account. All my Echos are also on one Amazon account. So the current behavior is that both houses act as one. Which is kind of neat in that at my real house, I can say "Alexa, turn on the gutter heaters." and they'll turn on at our snow house. But awkward when you're at the snow house and say "Alexa, turn on the kitchen lights." and way back at our real house, the kitchen lights turn on and nothing happens at the snow house. With a bunch of tricky naming, I *could* make this work... but it isn't very user friendly. The new v3 skill and Echo groups would help, but not enough. Each house has its own internet and internal network, so they're not on the same LAN.