This is a very complicated situation.
The money is undeniably a factor. If you have a baby, your will either have to do childcare, which is expensive and heart rending, or lose YOUR income, which is considerable. Living together might offset part of that loss, but not sure if it would equalize. Plus, babies can be expensive, and as they grow up, they become more expensive.
The other thing is, how do teh "baby mommas' figure into this. How's his relationship with them? He obviously parents his two children, at least in part. Is he paying childcare for them? Are the mothers reasonable people when it comes to makeing parenting decisions, such as who has the kids when, what school they go to, what constitutes punishable offenses and to what degreee, and more and more? I ask this because if you marry the father, you marry into his family, and that includes needing to interact with the baby mommas. And each one of them wants THE best for her own child and will maybe be in a natural position of opposition to you, once you bring in a "competitor" to their child. And the father, now has three mommas to balance.
Did this man ever marry any of these other women? Why is he not with them any more? Could the same thing not happen to you?
All questions that must be very distressing to face, but it should be looked at, square in the eye.