Great, cozy little space to stay. I visited during a heatwave and the basement stayed relatively cool, so it was a nice place to escape to, and the coolness made it easier to sleep. Mary's place is clean and simple, and she makes a kettle available with coffee and tea if you need a little cuppa to get you going in the morning.
Location is a quiet little neighborhood, short (~7 min) walk to Renfrew station on the Millennium line, which by the way does not go straight to downtown. You have to transfer to/from the Expo line at the intersecting Commercial-Broadway station, which in itself is not difficult, but does add a few minutes to the commute and can make it harder with travel bags. The 16 stops right in front and that goes to downtown and to 29th Avenue station on the Expo line, so that'll save you a bit of walking at the expense of a longer trip.
Entry is through a backdoor at the bottom of some steps, so you remain fairly isolated from the host; just keep a flashlight on you because the area around the house gets super dark at night, and the house is built on a hill so there are steps all around. Check in is as simple as it gets - just have Mary set a door code for you and you can use that to lock/unlock the door.
If you'll be using the shower, note that the hot and cold water indicators are backwards (the red is cold and the blue is hot). That aside, I very much enjoyed my stay and would definitely stay again.