I used to day trade penny stocks on RobinHood since it has no fees. With accounts below 25k you're allowed 5 day trades a week or something like that. Everything was fine for a few months and I was racking up a good amount of cash.. all the while making sure I stayed under the 5 day trade limit. Then one day one of the small companies on my watch list got HUGE new so I put more than half my account into that stock. And the stock EXPLODED upwards. In under an hour I had already tripled my investment and decided I wanted to sell. But when I tried to sell I got a message saying something like "day trade limit above allowed limit, buying and selling stocks restricted for three months." And this was all without a warning! I even checked how many day trades I had left before buying the stock, and I still had two. It was complete BS. So I couldn't sell... and I watched that stock crash over the next 24 hours and by the end of it, my investment was worth practically 0. After that, I am never going back to Robinhood.