to my knowledge, all that can be written off. but only if you do it properly and only to a point. keep accurate books and for the love of GOD - GET AN ACCOUNTANT!
get the phone book, call ten of them and interview them tell them what business youre in and pick the one you like best. in over a decade in the design/video business i have NEVER had a single accountant cost me more than he saved me or made me back. whether you are making $10,000 or $100,000 you might pay one $500 to $2000 for service, but i all but guaranty you it will make you back (or at very least save you) 2 to 3 times what you pay.
its just the way it works...