Check www.vrbo.com for your dates. homeaway.com is good, too.
I did a quick check for July 5-11 and found a 3BR at Myrtlewood Condos for $1075. Check the condos at Barefoot Landing, too, which will have many different price points. These are not oceanfront, but have pools and close to everything.
We stayed for a week in Myrtle Beach (for a Triple Crown tournament) and I found a summer week deal on a 4BR condo on Kayak.com surfing the net during the Christmas holidays.
My recommendation, book something....then keep looking. But expect to pay $$$$ for oceanfront.