Myself and my girlfriend will be going on a world trip soon. We start in Canada and will stay in Canada for 4-5 months before moving on to the U.S.

We originally intended to play the trip by ear and decide on the next leg of the journey when we arrived in a new location (if we liked it we'd stay longer, if not we'd move one, so wouldn't book the outward ticket till we arrived in a new place).

We've come to realize that one way tickets are a problem with customs and that its not unusual to be refused entry (or even allowed to board the outgoing plane) if you do not have a return ticket.

=====Our first problem is getting into Canada=====

- Do we have to have a return ticket or can will customs let us in if we have an onward ticket booked to the U.S in 4-5 months time?

- Will they still let us board the plane to Canada in the UK with an onward ticket from Canada to the U.S?

- It says we don't need a visa if we are in Canada for under 6 months, but since 4-5 months in Canada is a long time will we need to do anything else to please the customs officer?

- What about the next leg of our trip? Any problems for UK resident crossing Canada > U.S border? What would we need to satisfy U.S customs?

With the exception of a Brazilian visa application I have never been asked to produce an ongoing ticket to be permitted entry to any country. Since I live in Canada Canadian officials are not looking for such documentation when I come home. My suggestion is to avoid giving vague sounding answers when questioned; have a plan. You will have trouble if it is suspected that you are going to be seeking paid employment when not being entitled to do so. I have seen many people holding UK passports in the US customs/immigration pre-clearance area of the Toronto airport so it can't be too big a deal. When entering the US they will want the exact address (including zip code) of the place you staying for the first night.

Are you UK citizens or simply residents? It could make a difference.

If you haven't read the information on the Canadian Border Services Agency website, you should do so.
http://www.cbsa-asfc.gc.ca/noncan-eng.html

Thanks for the answers so far.
@laverendrye - I'm a British Citizen.

I have looked aty the CBSA website. It's quite vague:

"Have a valid travel document, such as a passport;
Be in good health;
Have enough money for your stay. The amount of money you will need can vary with the circumstances of the visit, how long you will stay and whether you will stay in a hotel or with friends or relatives. For more information, ask the Canadian visa office in your country or region.
Convince an immigration officer that you have ties, such as a job, home and family, that will take you back to your country of origin; and
Convince an immigration officer that you will leave Canada at the end of your visit. "

Of course it is vague. It is meant to:

1. Deter visitors who may be not be planning to visit as tourists, but to come and work or to try to stay permanently without a visa; and

2. Give immigration officers some leeway in dealing with them.

This is no different from the way in which the UK Border Agency treats general visitors. As an example you might want to read the recent account by a Canadian journalist of her treatment by UK immigration officers:

http://tinyurl.com/pycohd