American moving to Canada

Hi Everyone.... This has probably been posted so many times, but here goes. I am a Canadian woman and have been dating a New Yorker for a few years. He has a very good job in New York, and wants to keep it. His employer says he is fine to live in Canada, and continue to work in New York. We are both very close to the border. My guy travels across daily, to visit me. I go there as well. He wants to start looking into living in Canada, permanently,with me.
Eventually we want to marry, in the next year or so. I do have a good job here in Canada.

I know it can be a long process, and that's fine. What we don't want, during the process, is any trouble at the Border. We want both of us to be able to cross freely as we have been doing so, until the time comes that he is legal to live in Canada. I was thinking dual citizenship...not sure. We were considering seeing an Immigration lawyer in the Niagara Falls area, but maybe it's fairly simple and we don't need to waste the money. Any help or advice is appreciated. Thanks.