Assuming that $45,000 is your net business income (after deducting all business expenses - your Adjusted gross income (AGI) would be $41,821
Assuming - you do not itemize - but use standard deduction - and assuming that you are single - $5,700Personal exemptions - $3700
Your taxable income - $32,471
Your estimated federal income tax liability - $4,453
You will owe 15.3% self-employment tax on business income - $6,358Total estimated tax liability - $10,811
There is no state income tax in Florida.
If you have any qualified deductible expenses - your net business income will be reduced and your tax liability will be less.
Let me know if you need any help.