My dad owns an upholstery shop. He pretty much provides furniture with padding, springs, and fabric covers.
I would love to work with your dad to learn how to upholster furniture.  Recycling furniture is a growing market
It really is. Uphosterers, or trimmers as they are sometimes called, can always find business. People always need them.
It seems like I run into someone daily getting a sofa or dinning room chairs upholstered. Do you ever help him?
Sometimes I help him with the simple stuff, like seats. I'll help with the padding and cover them with either leather or just regular fabric
Have you ever help him recover any Mid Century Modern furniture? I love that period.
Yes! It is especially popular with scholars and museums. It is a significant design movement, really.