I found this on another forum:
In Section 5.1 of the Foreign Workers Guide, they explain what is not considered to be work for purposes of having to be issued a work permit:
What kind of activities are not considered to be work?
• An activity which does not really ‘take away' from opportunities for Canadians or permanent residents to gain employment or experience in the workplace is not “work” for the purposes of the definition. Examples of activities for which a person would not normally be remunerated or which would not compete directly with Canadian citizens or Permanent Residents in the Canadian labour market and which would normally be part-time or incidental to the reason that the person is in Canada include, but are not limited to:
• volunteer work for which a person would not normally be remunerated, such as sitting on the board of a charity or religious institution; being a ‘big brother' or ‘big sister' to a child; being on the telephone line at a rape crisis centre. (Normally this activity would be part time and incidental to the main reason that a person is in Canada);
• unremunerated help by a friend or family member during a visit, such as a mother assisting a daughter with childcare, or an uncle helping his nephew build his own cottage;
• long distance (by telephone or internet) work done by a temporary resident whose employer is outside Canada and who is remunerated from outside Canada;
• self-employment where the work to be done would have no real impact on the labour market, nor really provide an opportunity for Canadians. Examples include a U.S. farmer crossing the border to work on fields that he owns, or a miner coming to work on his own claim.
There may be other types of unpaid short-term work where the work is really incidental to the main reason that a person is visiting Canada and is not a competitive activity, even though nonmonetary valuable consideration is received. For instance, if a tourist wishes to stay on a family farm and work part time just for room and board for a short period (i.e., 1-4 weeks), this person would not be considered a worker. We recognize that there may be overlap in activities that we do not consider to be work and those activities which are defined as work not requiring a work permit in R186. However, the net effect (no work permit required) is the same.
I think the key word here in the 4th item is "temporary", so if you file your PR and have duel intent it might start to get a bit more complicated.
