Co-habiting partners can stay with a person lawfully admitted in a non-immigrant category indefinitely in B-2 status, which in the case of TN-1 would mean when you renew it, the B-2 status has to be reacquired I would imagine, i.e. you tell the agent at the POE where you enter.
http://travel.state.gov/visa/laws/teleg ... _1414.html
If the agent will give the partner TD, may as well get it I suppose but there's no real benefit as they have similar restrictions.
The problem is that it's unusual and that means problems.
As for health insurance, depends on what the company offers. DIY is very expensive.
When I lived in the US I never bothered to get healthcare, there was a co-payment or something and it was utterly pointless given how limited the coverage was. I got some travel insurance which would have covered really bad things happening to me and paid for everything else out-of-pocket.
I have to say I found doing that to be highly educational, because at one point I had to go to hospital and then I received this enormous bill. And on this enormous bill, 90% of the things listed on it had nothing to do with me. An extremely red-faced doctor at the hospital apologized profusely and my bill went from thousands and thousands down to something like $1,500.
I came to the conclusion that hospitals pile expenses onto people they think have healthcare (i.e. white people) and defraud the insurance companies to cover people who don't have healthcare, because usually you never see the bill unless the insurance company questions it. On my bill there were pages and pages of little things that I assume an insurance company wouldn't have questioned.
The one thing I do remember from the bill was apparently I had a breast biopsy at a moment in time that I was actually in the ambulance!
Steve.