I am married, so it might not be the same as being bf/gf but before we got married my husband applied for a joint credit card at Capital One and they gave it to me, no questions asked. He just provided my name. As long as HE was able to pay the bills, the bank didn't seem to care who also got a credit card. (Technically, at the time he applied for a joint credit card, I was not his wife yet, and I was still using my maiden name because I was unmarried. So, technically, he was creating a credit card for a person who doesn't exist yet - but the bank didn't ask for any documentation.)
After I came to visit my husband in Canada, we went to Royal Bank of Canada together and added me to his bank account, making it a joint bank account. They did need me to be physically present there (it could not be done while I was outside Canada) but as long as I was there to sign the papers and show them a photo ID (passport) it was ok. I didn't need to show them a visa or anything.
Regarding "visiting" Canada - at the border you don't tell them you're going to cohabit for 1 year. You are going to visit your boyfriend, and that's not a lie, right? Whether you later extend your visit beyond 6 months or not is something you can decide later - you don't have to tell them at the border exactly when you are leaving, nor are you legally obliged to leave by the date you say you are leaving, if you file for an extension.
I believe many people apply to extend their visitor status to achieve common law status. I think they may even indicate this when they apply for an extension. Often, people ask for an extension of an year and get it. Occasionally, they may get less time than they asked for. If you get less than six months, you can apply for another extension before that six months is up. Unless your extension is rejected, you don't have to leave - you can keep on extending and extending.
(note: extending your visitor's stay, and applying for PR (outland or inland) are two completely different procedures. One doesn't have anything to do with the other.)
Applying Inland - basically means you indicate (on the application form) that you want your application to be processed in Canada. You have to be in Canada the whole time and you can't leave the country, even for emergencies. (well, strictly speaking you can, but nobody does that because you may forfeit your application. It's not up to you - they decide and their decision is final.) The whole procedure takes around 18 months, and may take even longer by the time you apply - there seems to be a big backlog.
Applying Outland - means you indicate that you want your application to be processed in London, UK. You can do this even if you are in Canada, or China, or Antarctica, or wherever. It doesn't matter where you are. You can still come to Canada and leave Canada, it does not affect your application. The procedure will probably take a much much shorter time, less than a year for sure. I think some people who applied through the London Visa Office earlier this year already got PR and are in Canada.