A down-on-his-luck man is battling to find money to pay for his son’s emergency operation. It is not until he stumbles upon his long lost friend that his life changes for the better.

You have two inciting incidents

When his son needs an emergency operation
When he stumbles upon his long lost friend.

I would stick with the inciting incident which sets his course of action.
Here would be an example: (Your logline would be different of course)
—–
“When his son suddenly needs an emergency operation, a cash strapped (Give us an occupation) devises a plan to steal the money from a rich former friend.”

Hope that helped