gold-digger
A person who marries multiple spouses is known as a polygamist.
Golddigger.
In vast scale, these girls are referred to as "Gold Diggers" or Hasslers. In another scale, these girls are referred to as "Prostitutes".
rich
You call them 'The person I owe money to'
Ask them in-person for the money. Call or send a reminder for the money. Threaten to sue for the money. If they do not pay, go to your courthouse to file a claim in small claims court.
frugal miserly stingy skimpy parsimonious
umm by phone or if the question is meant to be (waht do you call a person with a lot of money) that answer is rich
Someone who needs money might be called destitute or impoverished
Poor
The person is a blackmailer.
a treasurer!