I'll be trying for the same thing, though for various reasons I probably won't be trying until mid-June.
My guess is there will be a one-time "lease fee", and it could be hefty - $200? (I have no basis for estimating this other than that I seem to remember that has been the going rate for upgrades to certain other units when they came out.)
CDH.
If it's $200, I'm not getting one. You could get a Slingbox Solo for that. And that doesn't even have a monthly fee.
And yes, I know that won't do HD, but at the rate my ISP is uping upload speeds (i.e. not at all), it will be years before I could stream HD.