The OP shouldn't feel she can't have kids because he has kids from a previous relationship
Plenty of people don't have any/additional children because they can't afford it. It's an unfortunate fact of life for many.
but they have a home theybdorn live there all the time
No, they have two homes, both of which they live in on a part-time basis (although granted, usually more part-time in one than the other).
She has every right to have w child regardless of whether he has previous
There is no 'right' to have children. We all have to make decisions we would rather not sometimes. Her partner may not want additional children. What then?
Usually they know if they send them in crap that dads feel guilty so it's their way of getting more out of them
Personally I send my children to my ex's in their old clothes because good clothes aren't returned. And like many, I haven't had a penny out of my ex in 10 years. I don't get anything out of him and statistically, neither to the majority of people (usually mothers) who should receive maintenance. Go figure.
She is asking for advice to help not you criticising
Actually, it is your post I was critical of, not the OPs. It is refreshing to see a second family take a look at the situation as a whole and try to work out how it will all fit financially. Too many times, new babies are born to families without any consideration of the overall impact whatsoever.