My yardman lawnmower won't start. I think it could be the starter or alternator. I just need some ideas before taking it to a shop. Maybe voltage problem. What is a common problem?

What is the engine doing when you attempt to start?

It clicks or something but doesn't turn over. My Dad thought it could be a voltage problem. My friend gave it to us. He had it running and it stalled. I think it was last running early spring.