Word or phrase used to describe someone who controls someone else through possessions or financial means

Question

Not sure if such a phrase or word to describe a person/actions actually exists. Have been using “to lord something over someone,” but this might not be the correct usage.

ex1: If someone pays for a vacation and subtly reminds you that they paid for everything when a choice of activities becomes a split decision, especially when the holiday has already commenced and there is no return/exit. This renders the original gift of paying more of a burden than an actual no strings attached gift.

ex2: person receives a gift of a new device from children and gives the older model to spouse, but when spouse tries to exercise control over older device the person reminds them that it is/was theirs and should still have power over it.

perhaps a guilt trip, but especially with monetary/possessions used to influence and hold something over someone.

Answer 1

Here, one is trying to extract their pound of flesh from the other person.

TFD(idioms):

your pound of flesh

If someone demands their pound of flesh, they insist on getting something they have a right to, even though they might not need it and it will cause problems for the people they are getting it from. 

She has appeared on breakfast television to offer support (in exchange for heaven knows what pound of flesh from her husband).

Note: This expression comes from Shakespeare's play `The Merchant of Venice' (Act 4, Scene 1). Shylock is owed money by Antonio, and attempts to carry out an agreement which allows him to cut off a pound of Antonio's flesh.

Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012

Answer 2

Although it doesn't describe precisely the circumstances you mention, I would suggest the other was acting in a patronising way. (US patronizing)

To assume an air of superiority towards; to treat or speak about (a person, etc.) condescendingly, esp. with apparent indulgence or kindness. (OED sense 6a)

It is normally a term which applies to non-monetary over-lordship, where unwelcome "advice" is given, or superior or condescending attitudes expressed

To assume or adopt an air of superiority; to act or speak condescendingly. (OED sense 6b)

Answer 3

This is an all-too-common phenomenon and it's shocking to me that no one has yet named it. Still I might call it a "strings-attached gift-giver". Related to the following:

no strings attached: Without conditions or obligations; without a catch.