How do securities companies make profits? What risks does he have?

Securities companies collect commissions from residents, or they can operate their own stocks, as well as consulting fees and underwriting fees. Its risks come from: the underwritten stocks cannot be sold, and there is not enough funds for underwriting, which leads to passive shareholding. After the stock went public, it fell below the issue price, which paralyzed the company's operation. What's more, the commission collected is not enough to amortize the daily expenses.