>with all the registration, taxation, regulation etc headache this implies!

It's not if you are in the US.

You will get a 1099 from where you worked, you write it on your 1040 and include the 1099 with your taxes if I recall from when I was an independent contractor for a while.

It takes maybe like 10 minutes extra and 1099-ing is incredibly common nowadays (unfortunately) so not a super weird case.

And it's not regulation. You don't need to worry about anything besides getting the 1099 like you would your W2s and appending it.