Money for temporary obedience

Story about some rich guy with BDSM fantasies who buys a temporary slavery (Let's say a month) from a girl that can't reject (Like needs money for a medical operation for relative)

I like stories with the end chapters, depending on the path taken... One branch would end in getting an obedient slutty ****, another one ends in love and sweet marriage, in third she hates you and never talk again, in fourth she kills you in ****.

Also, I'd prefer only one female character, with consistent character between different branches.

And pure 1st person male, with all decisions to be main character's decisions

I'd do that myself, but I make a poor editor, mostly because of my limited English skills