A man wants to pay me off to leave my girlfriend

From a male LIB reader

I've been dating this lady for about two years now and she has been pressuring me to propose. We are both 29 and sincerely I am not ready to get married but I do like her and want to continue the relationship but amazingly about a week ago I got a call from a man offering me N500, 000 to end my relationship with her. The man is my girlfriend's ex-boyfriend who went to America 7 years ago. He's back in Nigeria now and wants to marry her but she told him she's in a relationship with me and can't leave me. I think he believes he can get her if I'm out of the picture hence the offer. I really like this lady but N500, 000 is a lot of money, I'm tempted to take it, especially since I am not ready to settle down. If I take it would that make me a bad person? I want my girlfriend to be happy and getting married would make her happy, so I would be doing her a favour by letting her go I think.