There is usually a percentage of expenses that can be deducted for a home office. There are federal guidelines that have to be followed. The accounting method will also have some impact on the method used to determine what and how much can be used. it is far to vast of a question for a forum and you should seek guidance from a licensed tax attorney or CPA tax specialist.

Ideally no. You may be able to claim the portion of the apartment being used for the business only. But, this type of claim on a tax return will increase the chances of an audit of your return. Best to avoid.