Smileless2012
You need to listen and take on board what your D is saying Nana. The title you've chosen for this thread is 'Abusive relationship' and an abusive relationship is not good for your D or your GC.
If she's questioning them buying a house together then she's clearly not happy with the way he's treating her. Find out what she wants to do, then you'll know how best to support her.
This has the hallmarks of coercive control and the one being controlled is often eventually isolated from family and friends. Please be aware of this as you don't want to be in a situation where there's little or no contact with her.
Stress and a lack of self esteem are no excuse for belittling the mother of your children by telling her she's no good.
This is very good advice. Take it from me, I know.
Ignore advice to not take sides, your daughter needs you. Be there for her whatever she decides, but make it clear that you are there for her, not for him. Advice to stay neutral is bad advice, and believe, I know! Support your daughter.