I had an interview that involved two tryout days. I got paid $500 in amazon prime credit. Worked for me and the company, we got to really see what it would be like working together. I got to see the codebase, they got to see my code.
Always a red flag.
That is if you get over $600(the IRS rule was $600 in late 90s not sure now) in Prime credit it has to be reported.