Brokers and Spreads
A spread is a difference between a buy price (ask price) and a sell price (bid price). Whenever you place a trade, you create a small profit for the broker.
Some would-be brokers simply charge a fee (commission) for each trade. The broker disclosed the commissions in advance as per its business plan.
Commissions
Brokers also make money from overnight fees, as well as spread markups for quotes and by charging for deposits.
Additional Income Sources
Start small, use strong risk control, and monitor your forex robot regularly.
Conclusion