G.T.
If your parents wont have to bail you out and feel put upon by you having more children then I see no reason for their fears.
If you share with them all of your ups and downs and money problems you are giving them valid reasons to fear you may not be able to handle it.
Being mature and capable involves not letting your family know your minute by minute problems in your own immediate family. If you act like a child they will continue to treat you as such.
I would think long and hard about what you share with your parents and you will probably understand why they feel you shouldnt have another child, and maybe they are correct. No one knows us like our own parents especially if you have not cut the strings entirely and become completely independent of them.
Also people my age really see what an economic crisis our country is in and how bad the crime is and how bad the schools are becoming and it concerns us as parents and as grandparents. We are a little wiser by life lived longer and some of our fears and concerns for our grown children are valid ones.