What is a good age to have a baby?

I'm 21 years old and I hav a 10 month old...I heard all the same things when I got pregnant. I had and still have a very supportive family. I live on my own with my son and his father. We do support ourselves without the help of others he has a full time job as an electrician (he is only 20!) And I'm enrolled in school full time. We are looking to purchase our own house and move forward with our plans and goals. So my question is people who judge what is an appropriate, acceptable age to have a child?