Under US rules, Independent Contractors can be paid up to $600/year without "employers" reporting via 1099. No taxes withheld over $600 if they sign the form W9.

Your CPA/Tax Preparer is the best source for this answer, because if you pay a handful of models $200-$300 for a shoot during the tax year, that is easier for your CPA to support with a simple "I paid some models" line item on Schedule C, than say a dozen models being paid thousands of dollars each over the year with no paper work.

Over $600 in a calendar year, you need to get the model's SS number, and have it ready to report to the IRS their earnings on 1099 by January 31...

You'll recall, as well, this past January, PayPal and CCBill, et.al., were all abuzz over issuing 1099Ks for credit card processing over $20,000 for program sponsors. That was for "gross receipts" before fees and affiliate payouts, leaving the sponsor to need to report on his Schedule C the CCBill income, then stating the expenses of the CCBill fees and any automatic split payouts to affiliates for those sales.

As well as good ol' plain 1099s for affiliates of VOD sites like HotMovies, AEBN and DogGone for earnings over $600. And Amazon.com.

i got more 1099s this year than any year in the past.