How long do you see yourself working for us?

If grounds maintenance is a career you would like to pursue for a long time, you could reply with: "I see my career being in this field and plan to stay long term. As you can see in my resume, I am not a job-hopper and am a loyal employee."

If this position is a stepping stone and you want more you could reply with, "I love grounds maintenance and would eventually like to lead a team and end up in a managerial role. If that type of growth is something that I could experience with your company, I would be thrilled to stay very long term."