Moral dilemmas and temptations, duty and responsibility, power struggles, ego-related conflict

"Dirty" money is money or a gift that is tainted in some way. Sometimes it's the person giving it who makes it repugnant but often it has more to do with the way it was obtained or what it represents. For characters reluctant to take and benefit from a dirty gift, the offer would create a moral dilemma. Some specific examples of these conflict scenarios can be found below.

A person convicted of drunk driving wanting to pay for a wheelchair that the character's child needs after the accident
An absentee parent reentering the character's life and offering to pay for their upcoming wedding 
An abusive spouse or parent buying gifts for the character out of remorse
An absentee parent trying to make up for past disappointments with expensive trips
Regular income being generated for the character through a parent or partner's objectionable career (prostitution, the sale of drugs, human trafficking, etc.)
An inheritance from a mafia boss or lifelong criminal
Being given a raise or bonus for completing a horrible task
Receiving settlement money from a thriving organization that still engages in the unethical practices that hurt the character

Losing sleep over whether to take the money or not
The character's life being harder if they don't take what's being offered
The character feeling guilty every time they use the money or see the gift
Having to keep the source of the gift a secret from loved ones
Lying about where the money is coming from
Feeling indebted to the person (if the money is a gift or donation)
Hocking the gift for necessary money, incurring the giver's anger
Accepting a gift that comes with inconvenient or unexpected conditions