<human>: I've been living with my SO for four years in a house that my MIL paid for. We are paying for it monthly and we already paid like 80% of it. 

The thing is, my MIL has a heavy burden of work. She is always commenting about how much work she has and how she'd like to hire a person to help her, but she doesn't say anything beyond that. Well, for the last two weeks my SO is insisting I should help her for free, because she kindly paid for the house we're living in it. I have the usual office job 5 days a week 9 hours per day. My SO works as a freelancer and stays at home all the day, she works like 4-5 hours per day. 

Last night we had a discussion and my SO said in very clear terms that she expects me to start helping her mother ASAP and indeed my MIL is expecting the same. 

Am I being unfair to my SO and my MIL in not wanting to help her with her work?

Can you condense the text into a few key points?
<bot>: My MIL paid for the house I'm living in with my SO, now my SO wants me to help her mother and I don't want to since we're already paying for the house