Please keep this immigration forum about immigration topics, please find your answers to related questions elsewhere on the internet. (google).
Since this forum is used by many people to investigate if the TN visa or TN status is for them, I will give brief answers. But the answers really depend on your long term intentions. I will assume you plan to stay in US for 3 years then return to Canada.
a) In short, it is a hassle. US and Canadian governments make it a hassle because they don't want people to move cars across the border easily. I personally found it easier and cheaper to sell my two older cars in Canada and buy one new car in US when I started my TN. My mover gave me several examples of people that had successfully imported a vehicle from Canada to US, but the time, expense (taxes, repairs) and hassle was likely not worth it. If you have a friend or relative in Canada, you may want to "loan" it to them for three years and take a three year lease in US.
b) You need to hire a moving company that specializes in cross border moves. Keep a copy of the declaration of the "stuff" you brought into US as you will need it when you move back to Canada (for Canada customs purposes). There are certain rules of how "new" the stuff can be before importing or you will be charged import duties. I never declared "my stuff" on my initial trip to US on TN, as my stuff was moved about 2.5 months later. In my case my company provided a "relocation package" to help with the move details. It is always best to ask for this as part of the job offer.
Other "hassles" when moving to US on TN status:
c) Obtaining a US drivers license. In California, I had to do the written exam and driving test before they would give me a temporary license. Due the delays in California DMV, it took me almost two months (I tried to do it as fast as possible). I understand in New York state they will accept your Ontario Drivers license and give you NY drivers license. So it depends on the state. (search on Google)
d) Income taxes. In California, you have pay taxes on your worldwide income on the year you become a California resident. At the Federal Level they have "significant presence test" to determine if you pay for entire year or just portion of year (search on Google).
e) Credit History, since you are new to US and have no history in US, getting a loan will be a hassle. I suggest opening a credit card as soon as you obtain your Social Security Number. (even opening a US credit card can be a hassle)
d) Car insurance. Shop around, find a US Car Insurance company that will take your Canadian Driving history into account. (Geico or others)
e) RRSP - in California you will pay California income taxes on the growth in your Canadian RRSP. I recommend you hire a profession who specializes in Canadian/US Taxes. (good news is it is only California that does this, the other 49 states and the Federal IRS consider RRSP as a retirement account and will allow gains to grow tax free).
I am sure I am missing other "hassles", but you have to investigate on your own. Please keep this forum to Immigration related questions only.
