Income is technically tax free however if you have any ties to Canada (i.e wife that stays here, drivers license, home etc. - you can expect to be slapped with a canadian tax payment upon your return).
That statement above is incorrect. Tax information is online and available to read. They have it set up as primary, and secondary ties. Nothing states how many secondary ties one may have, it's taken on a case by case basis.
Primary ties may be a family living in canada.
Secondary ties may be bank accounts, a house that is being rented at fair market value, etc.