A business associate is (seemingly) making big $ with HFT (High Frequency Trading) – What do I need to know?

I’ve read the wiki’s/etc but what is the reality of this? He is using appropriately $600k but claims to have doubled it in the past 9-10 months and is now suggesting I get into it. I am your standard LT S&P ETF investor and would not want to use more than say $25k or so for this but want to obviously understand it much better first. Anyone here into HFT?