US citizens do not require visas to come to Canada as tourists. You automatically get 6 months entry IF they wave you through no issue. Meaning you are never guaranteed the full 6 months (or entry at all) but if they do allow you to enter with no issue and no specific date written, then you get 6 months. So yes, it's easy, because it's standard. There is nothing to apply for.
However, if you are coming on a visitor status you CANNOT say you are moving to Canada to immigration/border control. You are visiting. You need to show ties back to the US (job, lease, bank accounts, return flight, etc.) to show that you are indeed visiting and can & will return to the US before your visitor status is expired. Their biggest concern is people coming in and not leaving. If you cannot give them reasonable proof that you are planning to leave, rather than moving and potentially working (which is illegal), they have the right to deny you entry even if Americans are 'allowed' 6 months. It is always up to the border officer.
Yes, I have been asked many questions, more than once. I keep my answers brief and do not give more information than asked. Before we were married I did not mention that we were engaged, just that I was coming to stay with a friend. I did not want to get into unnecessary details. However giving too little information or not having a plan also does not look good. This is likely what put me into secondary questioning on at least one occasion.
Getting a visitor status extension (not visa extension) if fairly straightforward and only about $100. I've heard Americans get approved all the time, but I can't say how many of these were in my boat (married, wanting to apply for PR) vs. just asking for more time.
You should apply for your extension one month before your current 6 months expires. Once you apply you have implied status, meaning you can stay in the country until a decision is made, even if your current visitor status expires. However, that is ONLY if you don't leave the country. Once you leave, you lose implied status and are re-evaluated fresh next time you enter.
If you get an extension and it goes the same as mine did, your new 6 months of approved time will start from when they processed your application. For me this was 6 months from October, even though I applied in June (original status expired in July). So my new legal you can stay until date is April. Which means had I not left the country, I could have stayed Jan. 2017- Apr. 2018 with no issue.
However, I did leave the country for our honeymoon, so when I re-entered in September, I got another 6 months from Sept (exit date is now Feb., not April). This is because when you leave the country, you are no longer a visitor, therefore any extension of your visitor status is null and void. It's not the same thing as getting a visa with a set timeframe where you can come and go. [This specific paragraph I'm 95% sure of from info off this forum, but always double check with others. I am going back to the US for a work trip this month, January, so it really doesn't matter, I'll be exiting before either date anyway.]
We still haven't submitted our PR, but this time crossing the border I'll have a copy of the receipt that I've paid for the first part of it and copies of the many forms I have filled out (even though we haven't submitted them yet). I'm hoping that this will show enough intent that we are trying to follow the rules and I'm allowed back in with ease for another 6 months. From what I've heard paying the fees and having proof is a big help.
So, with all that being said, if you don't want to get married, and you do want to do PR and stay in Canada, this is what I would do:
Enter for 6 months, apply for an extension 1 month before expiring with the purpose of staying longer as a tourist with your partner, and once you hit the one year mark, apply for PR under common law. I'm pretty positive once you submit your app for PR you can also stay under Implied Status (assuming you don't leave the country). However if you apply Outland (you should), I don't know if I.S. is a thing because technically you are apply from 'outside' Canada (even if you are currently here). So double check that with someone else.
RE remote work and taxes: Yes, I work remotely here, which is legally allowed as long as you do not have Canadian clients (I don't). I am filing US taxes, and thought as a visitor that alone is fine, but upon looking further I think I will be deemed a Canadian resident for tax purposes even though I'm not for immigration (there are several rules of when you are/aren't a resident for tax purposes). Therefore I will likey end up filing for both countries and paying the difference. For ex. If I pay 20% in taxes to the US, and Canada's tax bracket for me would be 30%, I will first pay 20% to the US and then the remaining 10% to Canada.
The difference of Canada and US in taxes is that the US taxes Americans on their money no matter where in the world you are (taxed by citizenship, which is crap). Canada taxes people based on residency, which is both being physically in the country, or having significant ties to the country. That means you can be a non-resident legally (visitor) but still have to pay taxes because you've physically been here. It can also mean you are Canadian and have been in another country for a long period of time, but if you maintain significant ties (for example a house, rental property, a spouse living here, etc) you will owe Canadian tax. In any case, most countries have treaties so you are only paying the difference at least, not double.
RE finances: I've lived in a lot of countries and only sometimes had bank accounts in those places. So it's totally a personal choice. I did open a Canadian bank account because I needed lots of proof of relationship with my wife for our PR. But I rarely use it. Before I had it, I would either take out cash at a bank that has an agreement with mine (ex. Scotiabank is in agreement with Bank of America) so that there wouldn't be ATMs fees, or I would just use my credit card (which also does not get foreign transaction fees). All of my clients pay into a US bank account, so I just pay off my credit card directly from my US bank like I always do.
That was a ton of info but I hope it helps! Good luck
