I think paypal might be the best option you have if you trust it, aside from that depending on where you live and which exchanges you want to use than you can get CoinBase which is easiest option or you can use shapeshift for the fastest transaction but it will be crypto. I understand you are probably  curious about this because you want to do arbitrage trading but instead of the timing maybe you should also try to focus on fee because most of the time the withdrawal fee plus the trading fee eats up a lot of that profits when you are doing arbitrage, even if you find 3% difference it becomes 0.4% very quickly because of it. There you will need speed not to lose money but it wouldn't really help out that much if your arbitrage is too little. %2 difference usually loses you money instead of gain for example.