How much money do you need to start algorithmic trading?

Less than most people assume. Backtesting and paper trading cost nothing — you can validate strategies for months with zero capital. For live trading, the practical floor is set by share prices and sizing: with fractional shares, a few hundred dollars works; without them, you need roughly the price of a handful of shares of your chosen ETF. A common path is to allocate $500–$2,000 to a first live strategy — enough that results feel real, small enough that a full drawdown is tuition rather than tragedy. Platform costs matter more at small sizes: a $10/month subscription is 12% a year on a $1,000 account, so size accordingly.