Check with your accountant if you don't want to end up in federal pound-you-in-the-ass prison. You really only get to right off a portion if you also live there.
Relax. It is very unlikely that you will end up in prison unless you hide lots and lots of income and lie about it. And I am not a CPA (Required Disclaimer), but this is my understanding...
To claim a home office, you do need a room that you use for business (so that cannot be your bedroom or living room which you use to sleep/watch TV in, etc.), but could be a spare bedrooms, study, etc.
You take the square feet of that room as a percentage of the square feet of your home. So if you room is 100 square feet, and your home is 2000 square feet, you use 5 percent. Then you can add up your utilities, repairs, mortgage/rent, etc., and claim 5 percent of that as the home office deduction.
So no, you cannot take off all of your home expenses. But you if you spend $2k a month for rent/mortgage + utilities that would be $24k times .05 = $1200 - maybe enough to knock you down a tax bracket... This is legitimate. I would assume the IRS would like it since you would certainly have much higher office expenses AND deductions if you rented an office elsewhere.
I have read that home offices may raise a red flag, but that doesn't mean you will be audited. And if you are audited, and you simply claimed the deduction you were entitled too, then you should not have any problesm.