Potty Training?

Kayla • I`m 22 years old, married, have an 19 month old son, and due March 14th with baby #2.
What is the appropriate age to start potty training? My son just turned 18 months and everyone is asking how potty training is going.. I have tried to start with him but I really feel like he's not ready. But everyone acts like I'm a lazy mom because he's not potty trained already..