A few brokers offer APis such as TDAmeritrade, and Interactive Brokers. IB has 10k minimum opening (though I believe you can transfer some of that out after).
More importantly to be a pattern day-trader and get the 4-1 margin you have to maintain a minimum account of 25k.
To your second question - no not really. HFT works by scalping a stock for pennies - buying and selling (tens/hundreds) of thousands of shares for a very short timeframe (seconds, minutes, hours?) (Tangentially look into the 'sharpe ratio' on wikipedia)
I don't think you can compete in the HFT arena - I would personally recommend looking at medium-term strategies and possibly using options for leverage.
More importantly to be a pattern day-trader and get the 4-1 margin you have to maintain a minimum account of 25k.
Also you should check out marketcetera http://www.marketcetera.com/site/ - though I don't have first hand experience with it.
To your second question - no not really. HFT works by scalping a stock for pennies - buying and selling (tens/hundreds) of thousands of shares for a very short timeframe (seconds, minutes, hours?) (Tangentially look into the 'sharpe ratio' on wikipedia)
I don't think you can compete in the HFT arena - I would personally recommend looking at medium-term strategies and possibly using options for leverage.