I am looking into starting a new business for photography and wanted to see if theres a clearly defined list if things I can write off for it. I'm assuming I won't make any money for a while either so can I apply those writeoffs to my spouses income?
The comment on the question "ask your accountant" is spot on. In the United States, photography is one of those things where a lot of part-time semi-pro folks can get into trouble for deducting what are essentially hobby expenses. The IRS will start noticing if your business continuously operates at a loss and you never declare any profit that can be taxed.
That said, here's a partial list of things which could be deductible for a pro photographer in the US (disclaimer: I'm not an accountant or tax professional, but am passing along what my professionals have told me):
This is one area where it's worth the investment to talk to a tax professional. A competent accountant should be able to help you understand what can be deducted and what documentation you'll need.
I was going to add a comment above but decided that an answer may be better. And I'm going to assume you are US based
What sort of business are you starting? LLC (various types), Sole proprietor, corporation? This determines how your tax is treated and whether or not you can use your spouse for write off as part of a dual filing.
As per the comment, get friendly with an accountant. I have an LLC (not photography) and my accountant has been very useful.
Even if you do get an accountant .. go visit NOLO and take a good look at the bookshop section. There are heaps of resources on starting a small business.