Can Canadians enter Belarus with no visa?

So, can a Canadian citizen just land at Minsk without any previous paperwork, and be awarded a 5-day visa?

There is no such thing as a 5-day visa. You enter visa-free, with no prior paperwork.

a Canadian citizen can enter Belarus "visa-free". What's the exact meaning of this?

It means you enter without a visa - in other words, present your passport and get stamped in, just like when travelling to the US.

You cannot transit Russia on the way to/from Belarus, and have to both enter and exit through Minsk airport. If you overstay due to illness (for example) you need to supply evidence and obtain and exit visa, which you can then use to exit anywhere

Is there a cost?

No

But the consulate of Belarus in Canada seems to not mention this and does mention support papers sent in advance.

That is if you want to get a visa on arrival, which you no longer need if staying for max 5 days.