I am a massage therapist. I work at client's houses only. I do not have a main location of business. Can I deduct car and parking expenses?

I understand that if I had a main location of business, I would be able to deduct mileage between the main location of business and the client's house. But, in my case (not having a main location of business), I am not sure if i can deduct mileage and parking expenses.