Make it worth your time when you price it. If you don't you'll be beating yourself up every time you cut it and that will make the whole job that much more difficult.
How about a self-propelled walk behind sickle mower or a brush cutter? It would be an investment for just that one job but if the job is priced right it could be worth it.
You could send one man out to do it. Of course it all depends on the severity of the slope if the cutter would even work.
Hopefully you are at the point with your business that you can walk away from a job when it doesn't feel right.