Ask HN: What are the hurdles to developing and selling an electronic product?

I'm considering developing an electronics product. I would be designing and manufacturing custom PCBs that are fairly simple. Things like wifi would be handled by existing modules.

For sake of simplicity, let's pretend I'm going to develop a custom PCB with a few buttons and a display and maybe wifi with an ESP8266 and put it in a custom enclosure.

I know there are things like UL certification and such. Do I have to deal with any of that? Can I just develop this product at home and start selling it?

I'm in the US.