Speaking from personal (Nasdaq, not scalping) experience, I think that if you are starting out with a small account, and expecting to withdraw enough funds every month to live off, and at the same time steadily grow the account, then you will potentially be putting yourself under WAY too much pressure, most likely leading to overtrading or taking on too much % risk per trade. In order to practise some sort of emotional detachment (a pre-requisite for successful trading IMO), you just don't want this type of pressure daily. Also, drawdowns on the account are inevitable, and can cause emotional chaos if under huge stress to produce profits. I would say that, for my moderate overheads, I would need an account size of £50,000 to trade full time, and even then I'd want other SOIs to weather the bad times. Having this account size would allow me to diversify my strategies, in an attempt to reduce drawdowns and produce a smoother P&L.
(My comments don't apply to scalpers who generally have a steadier equity curve, as their amount risked per trade is often negligible)
rog1111