The IRS expects taxes to be paid as income is earned or received.
Assuming - you are expecting gross income for 2009 to be $30,000 and your qualified business expenses $5000 - so you estimated net income would be $25,000
If you are single , standard deductions, no dependents, no other deductions or credits - your will owe self-employment taxes $25,000*15.3%=$3825
your taxable income will be $25,000 - $1913(half of self-employment taxes) - $5600(standard deduction) - $3600(personal exemption) = $13887
and your estimated income tax liability is $1666
Your total estimated tax liability would be $1666+$3825=$5491
Generally, you should make estimated tax payments for 2009 if at the tax time you will owe more than $1000 and the total amount of tax withheld and your tax credits will be less than the smaller of:
-- 90% of the tax to be shown on your 2008 tax return; or
-- 100% of the tax shown on your 2007 tax return (110% if your 2007 adjusted gross income exceeded $150,000).
Michigan income tax rate is 4.35%
Some cities have additional taxes - see here - http://www.crcmich.org/TaxOutline/Income/ucit.html