It really depends on the investment company, but here are some generalizations:
Brokers
often make a commission when they execute financial transactions, but they usually have some associated fees too. Zero-commission brokers have various other ways of making money to compensate for their lack of commissions.
Financial advisors
generally make money off of fees, commissions or a combination of both. While fee-only advisors might charge you more, their compensation structure helps avoid conflicts of interest. This is why most fiduciary advisors don’t take commissions.
Other investment firms
will make money in ways that make sense for their respective industries. Don’t expect a real estate firm to make money the same way a gold IRA company does.
Regardless of the type of company you’re dealing with, it’s smart to investigate how the firm makes money and how that might influence its services.