Tips for starting your own business..while working FT elsewhere?

Dh and I have been thinking of ways to make extra money to save. He works part time and takes care of our son..I work full time but have good hours. I paint..and have sold several...I was thinking of painting canvases (reg size or even cheap mini ones! He is thinking what he could make. But we would sale things on amazon, etsy, etc?

Anyone do this or something similar that has advice..or input would be appreciated. Any advice is appreciated! I see pros/cons both ways and I'm unsure.