In “My Madonna”, by Robert W. Service, the narrator describes how he “hailed” a prostitute “from the street” and painted her portrait. Having added a halo to the original painting, the poet/narrator sells the portrait, which now hangs in a church” Where you and all may see”.
It is merely my interpretation, but the line “ And I sold her and took my fee”, suggests to me a connection between the subject of the painting (a prostitute) and the poet (over and above the obvious fact that he painted her portrait). Both are selling something. In the case of the “Madonna” this is sex, while the poet is selling the prostitute’s painting and, in a sense the girl herself.
You can find the poem here, https://www.poetryfoundation.org/poems/46644/my-madonna