The 'non-rust' part is the alloy cutting deck. Steel cutting decks can rust quite quickly if left with wet grass clippings stuck to the inside surface. Depends on where and how the mower is stored.
Many mowers have a little hole for garden for a hose on the top surface of the deck, just run it for 30 seconds with water squirting in and it self cleans.
Had my $299 ?mitre10 mower for 6 years now, it's defintiely not alloy nor plastic, so i think steel, never cleaned any wet grass off it (or maybe I only mow when it's not too wet because of boggy ground?), no problems. just getting hard to start.
If you aren't cutting wet or long grass and you store your mower somewhere dry, you are unlikely to have a problem with rust. The deck on a new mower generally has a protective coating as well.
RE getting hard to start - the spark-plug and air filter are easy things to check/clean. The filters are often foam rubber and easily blocked by dust etc. I wash my filter out with water followed by methylated spirits once each year - wearing gloves of course and allowing the meths to evaporate before reinstalling it.
A dirty air filter will often cause the plug to foul. I use an old tooth brush and carb-cleaner to clean the plug.