Kim, I used to work for H&R Block. Don't knock them. True, during tax season they hire a lot of part-time preparers whose only training is their 18-week course, but they have a core of full-time tax preparers, and most are Enrolled Agents. People with Enrolled Agent status are the only people who can represent you in a case before the IRS.
Enrolled Agents have to know all parts of tax law. The Enrolled Agent test is an extremely difficult 3-part exam. Miss any part of the parts and you have to retake that part of the exam. After you pass, you have to take 72 hours of classes every 3 years to maintain current on tax law.
A CPA cannot represent you at the IRS unless they are also an Enrolled Agent. So, you shouldn't call just any CPA for tax advice. Don't ask for a CPA who is a "tax expert." Anyone can call themself a tax expert. Ask to speak to an Enrolled Agent. If they don't know what you are talking about, hang up!
No, I'm not an Enrolled Agent. I took several tax courses, but corporation taxes just did me in! But I have been a tax preparer since 1984, and I can tell you what everyone above has been trying to get across to you is spot on. You can take the mileage deduction for your business even if you don't have a qualifying home office.
NOTE: I'm not on the forum every day. If someone comments on my post, I might not reply right away. I've been a shopper since 1991. I've never done any work for a MS company in any other capacity.