mazda has rust problems as well, but i live in the dried up place known as texas so its not of major concern here. just check the car well before buying, however you do live in canada so i am sure you know that from experience. however other than some minor rust issues these cars are decent cars. they do win almost every single head to head comparison and get decent to great fuel economy depending on engine/year and transmission you get. mazda cars are well screwed together and mechanically are very reliable and last a long time. HID lights (the bright white ones) that come on top trims are expensive to replace($100ish USD around where i live) so avoid them if your on a tight budget. some of the older 2.3L motors (up to 06) have a flaw that can allow an oil seal to get sucked in and ruin the engine due to fatal oil leakage, however this is very very rare and you should not be concerned about this if the car has been maintained, mazda is aware of the issue and all 07 up 2.3L have been fixed and a respectable mazda dealer should work with you if needed. there is a recall in the usa on some 3s and 6s for a power steering issue check if a car your interested in has this recall in canada. otherwise i have had my 08 3 with the 2.3L for almost a year and its been a great little car. oh and check the motor mounts (theyre cheap to buy) there is a known issue with the 3 with passenger side liquid filled ones leaking and failing causing excessive idle vibration and that could eventually lead to more issues later on if left un fixed, however its not a major issue
altimas are decent cars, but yes where rust would be an issue the floor pans could rust, plus the 2.5L motors have a known problem with failed catalytic converters and this seems fairly common. the v6 altimas however are made really well and run forever the 2.5l motor itself is good but the exhaust sucks and this is usually due to valve cover leaks that go unfixed.
honda accords are alright cars however they eat cv axles and have internal transmission issues. thats all the major issues i have seen working around them at a parts store. all front wheel drive hondas like to eat cv axles its an odd issue with them
toyota camrys and corollas are good as well but the 4 cylinders do develop odd evap and egr issues that sometimes cannot be fixed and lead you on a never ending parts chase. the 1.8L motors seem to be worse than the 2.2/2.4 though. (thats US models though i am usnsure if canada emissions on these cars even have all the same components)
i must give you my personal heads up and say avoid chrylser cars, so dodge, chrysler etc. they are low quality especially compared to japanese competitors.
fords fusions are basically mazda 6s and run well newer focus's are good 07 and up.
