1. when I cross back to Canada does Canadian customs tell US customs, when I cross back into Canada? If so how long does it take US customs to get this information?
not yet, but they are working on it.
2. When Canadians can visit 6 months out of the year as visitors. Does it count from January-December as a calender year, or does it count from when you cross as a year? For example if you cross in June the calender year would be June08-June09?
it depends who you ask. You can ask 3 or 4 different CBP officers and they'll all give you a different answer. Same as for people on an internet message board. Its either 6 months per calendar year, or its 6 months per visit, take your pick, take your chances.
3. Can Canadian citizens join things such as the US Air Force or Coast Guard, or do you have to have a green card or be a resident citizen of the US?
you have to have a green card to join the US military
4. I used to sell real estate, and also work as weatherman. I dont see any of this stuff listed in TN visas under NAFTA, is there any types of visas for this stuff?
nope
Canadians are not eligible for the Green Card lottery.


