I think you will learn to dot the I's and cross the t's in agreements, your h sounds like he will just take advantage.Dreadful when it's his child.
The financial implications of being single at our age (I,m much older tho but was a litle older than you are now when it happened) was and is my greatest concern.
It somehow seems the wrong end of life to be scrimping and poor.
I truly hope God sends an angel to watch over you or at least opens a window.