Could you offer to let him play in your garden? We used to have a little dog, Titch, who ended up being alone when I went back to work. On my first day, i asked my neighbour to tell me how my dog coped. Titch was outside, but free to roam the garden and go into the laundry and the workroom under the house.
Well, my neighbour told me Titch had cried all day. I was horrified, but she offered to let her sleep on her porch while I was away. She was a widow and a bit lonely. So that is what happened. When we all set off to school and work, Titch trotted off to my neighbour's place and everyone was happy.
In return, I used to set my neighbour's hair every Saturday, and dye it when necessary.
Another thing your neighbour could do, would be to set one room aside for the dog during the day, and have only the dog's toys and bed in there. larger dogs seem to have strong bladders and don't need to pee for hours and hours.