Advice for a first time seller?

I was speaking to my Mom on Sunday about selling stuff online. They have lights in their home that she's thinking of selling on EBay or even Etsy (they are technically vintage). I did not have a lot of advice regarding this other than the fact that people love to buy items from sellers with positive ratings and feedback.

For those of you that have Etsy shops (I know a few of my friends do) is this the case on Etsy as well? Would you ever buy something from a brand new shop/seller? I've purchased a few things on Etsy that I've been very happy with. I had a very good interaction with one of the artists I purchased a pin from around Christmas. I like that personal touch.

Also saw this on Etsy today and just had to share: