Single parent dating: when is it a good time to introduce a new SO to your child?

I am a single mom of a 4 year old daughter. In 18 months since splitting from her father, I have not had a serious relationship.

I met someone a month ago who has become a significant part of my life.

For those of you who have experienced this, what is your advice on how to introduce a new love to your child? When is it ok to have the person sleep over?

My goal as a parent is to make conscious decisions in regards to my adult relationships.

I have seen the opposite extreme of this situation, where the parent was not consciously looking out for the child’s best interests and moved in with a new SO with no regard for how it may affect the child.