Is a plane ticket the only proof that I will exit the USA when applying for a B2 American Visa?

I plan to spend a month in America, followed by 5 Months in Canada on a canadian work visa, then travel back over to america for another 3 months before flying to England. But I will be crossing the american/canadian border in a car. And I don't have evidence to support my promises of leaving the country when I enter the first time (like a plane ticket). Is there other ways of proving this?Is a plane ticket the only proof that I will exit the USA when applying for a B2 American Visa?You don't have a job waiting for you at home? A house payment? Car payment? Family? All these things can be used as "proof" that you're coming home.