Based on your statements, 1. You are renting a bedroom in a house and allowed use of some other space. 2. You pay separate rent (fee) for use of a room that is used 100% for business. 3. You do not own the house.
Is the house owned by a relative or a 3rd party? Rent is FMV (fair market value)?
Is the type of business such that you don't meet clients or 3rd parties? Online type of business?
If the answer to these questions are 3rd party and FMV rent; I would say you could deduct the rent of the room used 100% for business. I don't think you would have any other expenses such as electricity, etc., just the rent. However, if you pay a separate fee for utilities, then that would be deductible, based on either sq. footage, or if the fee is directly for the utilities of the office space.
I don't see this as being any different than renting space in say an office building; except there is no entrance for public unless invited in. That might make it a "Home office". But, you are paying a separate fee, so there would be no allocation based on sq. feet as you are paying directly for the footage.
If the scenario is any different than what I based my opinion, that may/may not change the answer.
This may help you and/or provide links for further reading/research
https://www.irs.gov/publications/p535
**Disclaimer: Effort has been made to offer correct information; but due to the discussion forum limitations, the poster disclaims any legal responsibility for the accuracy of the poster's response**
