These are the parameters:
You live on 1/3 of an acre (not all of which is grass of course). Yard is a rectangle and there are no hard geometries to work around. It takes you, an adult of capable skill, about 45 minutes to mow the lawn with a push mower. This 17 year old has an old driving mower from his dad and can mow your lawn in about 30 minutes.
No bagging of grass, just mulching. No trimming or edging. Just the mow.
This 17 year old is a boy from the neighborhood.
If it makes a difference, this is in Idaho.
This is based on an actual boy in my neighborhood.