The Japanese brands are generally a safer bet for reliability. Toyota is one of the best reputation wise but that comes with an increased price due to that reputation.

A manual transmission is best for reliability IMO, but if for some reason you really must have a automatic look for one with a standard auto transmission rather than a dual clutch box or a CVT. Run away from VW dry clutched dual clutch and Ford Powershift transmissions.

Ideally you would have proof of regular servicing, though a completely good record is harder to get on a low budget. Not only do you want it to have the engine oil changed at the service intervals (depends on the vehicle but often ~10k km) but also the other regular stuff that often gets ignored - e.g. brake fluid, coolant, transmission/diff oils, brake pads/rotors. Keep an eye out for big ticket maintenance items such as timing belt changes (typically due around every 100-150k kms) as these are expensive so are often ignored at the risk of major failure.

If you’re not confident in spotting issues try and bring along a friend or acquaintance who is more familiar with cars to look it over.

Since you’re in Canada where I believe road salt is common check for rust under the car and in places like wheel wells where moisture is likely to be trapped. It’s hard to avoid some rust in such an environment but you don’t want rust holes anywhere or large sections of flaking rust.