If the nature of your trading activities doesn't qualify as a business, you're considered an investor and not a trader. It doesn't matter whether you call yourself a trader or a day trader, you're an investor.

I didn't say that, IRS did, here:

https://www.irs.gov/taxtopics/tc429

Generally speaking, people who lose money want to be called traders so they can claim it all in one year, and people who make money want to be called investors so they don't have to pay self-employment tax.  Are you sure you want this client?