Can I write this off in my taxes?

I'm a 20 year old Youtube Partner. I create videos and earn some revenue from doing this. I got a 1099 form today and was wondering about the following;

The majority of my videos have to do with testing the durability of electronics. For example, in 2013, I have purchased probably 10-12 iPhone's for my videos. I would individually test each iPhone in a serious of different destruction tests. What I'm wondering is, if this is something I can consider writing off as a deduction or not? Because I did spend quite a bit of money into these iPhone's to earn somewhat of a profit.

Now, the only issue I have is, I don't exactly have all the receipts of these phones that I purchased. Some were off eBay, some directly from Apple, while others were given to me. What do I do in this case?

Thanks.

Added (1). The iPhone's would be sold as parts for a tiny fraction of the price. And yes, this is something I do for a living.

If those iPhones are used EXCLUSIVELY for the testing videos, you can deduct that as a legitimate production cost. When you sell the phones, you have to claim the sale as income. Keep in mind that you have to depreciate business equipment over 3 years.

See a professional tax preparer or learn the rules.

Are you trying to make a living off of your videos, or just pick up some spare cash?

What did you do with the iphones after you tested them and made the videos?

That info is needed to answer your question.

Yes, obviously these are used for testing and rarely actually used for personal use
since you also sell them for parts they are a part of your cost of goods
receipts will be required if you are audited, so if you claim some that you can't prove the purchase, they will be denied in the audit

You can deduct ordinary and necessary expenses, yes.

The money you got form selling off the phones and parts is income as well. Without receipts, no deduction. If the were given to you, no deduction.