In the Myrtle Beach area you will find quite a few landscape supply companies, and small nurseries, that provide a variety of mulches and plants. Cypress, hardwood, and pine straw mulch are the most commonly used.

I am not sure about the compost. Some of the smaller nurseries may carry that in bulk, otherwise you will need check with the retail stores or make your own.

Try checking with the local landfill for mulch. I"m a little further south, but can get great mulch at the landfill for cheap! It's a great product and you get to help recycle at the same time. :)