Having baby for my sister

I know the title sounds bad , but my sister is gay and she is married I love them so much they want a baby so bad and it’s absolutely expensive to hold & for someone else to hold the baby . I’ve told her so many times I can give you a baby me & my husband (chris) said we would both love to help her she messaged me today saying if I can still do it and I told her I would love to give you a baby . My other sister thinks I won’t be able to go through with it but honestly I am I want to help her out with this babies are a gift from above & a blessing I know the baby will be taken care of so well has anyone done this before ???