@Nathan S. The IRS has a basic standard deduction now for a home office. The "I'm going to get audited for taking a home office deduction" fear is overblown. You're losing out on a ton of savings by not utilizing this!!!! So get on it! Yes, the deduction states it should have a separate entrance, etc, but they've long ago realized times have changed, and so, as long as you're not deducting a huge % (i'm at 5% of my sq. footage) of your square footage as your "home office", you're safe.
The mileage deduction is another one where you can either use the standard deduction or calculate the mileage and use the .50 cent (think is is the going rate, I'd have to check) per mile the IRS allows. Any time you use your vehicle for business, you deduct the expenses (gas, oil changes, etc). You can't, however, deduct payments, unless the vehicle is used EXCLUSIVELY for business (realtor, business leases the vehicle for you, for example).
I'm not a CPA, but I do have an accounting degree so I understand the BASICS of these deductions. I'm assuming you have a CPA since you're in REI. If not, get one. Period. One that specializes in REI. In the long run, the money you save by having one will more than outpace the cost of paying for one!
All the best in 2017!
Aaron