First of all he need to file tax return - you will use schedule C for your self-employment income and expenses - http://www.irs.gov/pub/irs-pdf/f1040sc.pdf and calculate your net income. You net income from self-employment is a subject for 15.3% self-employment taxes and should be calculated on schedule SE - http://www.irs.gov/pub/irs-pdf/f1040sse.pdf
You will use 1040 form - http://www.irs.gov/pub/irs-pdf/f1040.pdf for your tax return - following would be important entries:
The key point is to determine qualified business expenses and to keep a good record.
What may be qualified expenses for him? Tools, materials, special clothes, safety items - glasses, boots, etc. Travel expenses - he might drive his car from place to place. Cell phone expenses - he likely getting customer's calls.
You may want to become familiar with the IRS publication 535 - http://www.irs.gov/pub/irs-pdf/p535.pdf
and the IRS publication 334 - http://www.irs.gov/pub/irs-pdf/p334.pdf - see chapter "Business Expenses"
To be deductible, a business expense must be both ordinary and necessary. An ordinary expense is one that is common and accepted in your industry. A necessary expense is one that is helpful and appropriate for your trade or business.
You can deduct all of your travel expenses if your trip was entirely business related. If your trip was primarily for business and, while at your business destination, you extended your stay for a vacation, made a personal side trip, or had other personal activities, you can deduct your business-related travel expenses. Please see for reference IRS publication 463 - http://www.irs.gov/pub/irs-pdf/p463.pdf
Travel from home to your work place is always considered a commuting travel and not deductible. Please see IRS explanation here
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I would also suggest to look at the schedule C - http://www.irs.gov/pub/irs-pdf/f1040sc.pdf - part II lines 8-28 - see the list of most common deductible business expenses.
Please let me know if any clarification is needed.