It's cockney (i.e. from London) rhyming slang for earning money. Bunce is derived from bunsen burner (a common piece of school laboratory equipment that produces a single open gas flame and named after Robert Bunsen) and this rhymes with earner.
It was toughwork but I was earning a good bit of bunce .
(Noun) Lindsey bunce is a great singer and a beautiful girl. She has brown eyes and long brown curly hair. She makes an amazing friend. Shes alays there gor people she loves.