I may want to start doing paid drone work.  Have been told that to do that need to be a licensed drone pilot.

How much $$ does that cost and what's involved?

It's called a Part 107 Knowledge Test / Certification. You can find some more information about the test at the following links. I believe it costs around $150 to take. There are a lot of videos on YouTube about it as well.

https://www.faa.gov/news/fact_sheets/news_story.cfm?newsId=20516
https://www.faa.gov/uas/getting_ ... s/becoming_a_pilot/

A Part 107 license would be needed to fly for any sort of monetary gain in the United States. The links that Adam Flurk provided are a good starting point.