If the money was earned as an independent contractor, and you are filing a single person with ony a standard deduction, then my estimate of about $7400 in additional taxes for federal income, social security, and medicare would apply.
You may be able to offset some of this income as an independent contractor. For example, if you used your car to drive around real estate clients, you could deduct auto expenses
based on a per mile expense or a pro rata portion of your total car expenses. You may also have deductions
if you maintain a home office, or other costs associated with earning these profits.
But if the $23,000 was pure profit, then you are looking at around a $7400 tax bite. If, with your other jobs, more was withheld than was necessary to cover that income, you may be able to offset some of your additional taxes with that money paid.
In other words, your total tax bill would be around $11,500 minus whatever you paid in withholding
at the two jobs that withheld taxes.