1 year Visa in the Schengen, need proof of onward travel?

[teneighty]

I have recently received approval for a 1 year working holiday visa for Belgium. An affordable and interesting way to get there which suits me nicely is Vancouver to Montreal to Paris by air, and to Belgium by train. It appears from the wording on Belgium's website that they don't require me to have a return ticket, at least not for the application, but that I have sufficent resources to purchase one. Since I will enter the Schengen Territory via France, I need to know what the officials in that country will say if I arrive with a 1 year visa in a neighboring country, and no return airfare.

I checked and for tourists and business travellers, France requires proof of onward travel, but I don't know about long term visa holders. I don't seem to be able to purchase round-trip airfare online for a 1 year trip, but I could go for an open return if the airline offers one. What could I run into, and how do I avoid problems?