If you use map.search.ch then you can type in the address of any apartment you are looking at, click on the checkbox on the left that say "Shopping/Services" and look to see if any little yellow shopping carts appear near the circled apartment location.

As for trains, the fast intercity trains don't stop in Renens (but they all do in the main Lausanne station), but there are probably a couple of regional trains per hour that stop in Renens that will get you directly to Geneva airport in about 45 mins or so. Check the SBB website for schedule details, and click here to get a pdf of the map of the train network so you can get an idea of where everything is located.