Opinions please..🤔🤔

So my best friend will be having her baby in June this year, and will need someone to watch her in July. She couldn't find an affordable daycare. Well 4 days a week from 7 to 2:30 was all she needed. I am off work during that time, and we could use the extra money so I told her I would help her out. I talked to my boyfriend about it and he got so mad saying we are not gonna have a baby here. I told him I could go there and watch her, and it would be an extra $540 a month for us. He was so mad about it and couldn't give me a legitimate reason why. Is it wrong of me to go ahead and do it for her?