As a prop trader I never kept more than about £30,000 in my account. That was plenty, the prop firm gave me additional leverage. But that's all the risk I put on the line. But I was day trading I could look to make or lose £300 a trade multiple times a day and an average good day was 1-2k and average bad day about 1k.. but fortunately had a high percentage of good days. If your overheads are lower and can cover costs making 500 or so a day then account can be smaller. Your account size doesn't dictate how good you are as a trader. If you can't make at least 500 a day I wouldn't bother going "pro" anyway.