I'm sure you can stay there for 6 months without any problems. I did it in Vancouver. As for a job, just look for something under the table. It makes everything easier. At the border, don't tell them you are planning on living in Canada for 6 months though, just say you are planning a trip for one month, stay for six, and then tell the U.S. Border whatever you feel like when you get back. They don't communicate and as long as you haven't done anything illegal, you will be fine. It worked great for me.
I've had Canadian friends denied access into the U.S. and American friends denied access into Canada when the border patrol thought they were dirtbags, unemployed, and possibly living/staying with a significant other in the said traveled country. So lie, it's easier. You are an American citizen, they'll let you back in.