Printing a binder onto sand would work pretty similarly to SLS printing. HP also have a line of printers that print a binder onto a powder medium to create parts. Not sand in this case but same basic concept.

The problem I see here is that this method is that you would end up with a mold that's full of sand. Parts produced by SLS and HP's printers are not hollow, they are full of the unbound or unsintered powder. Investment casting or similar with regular PLA/wax FDM printing is probably your best bet. If you've got money to burn take a look at SLM (not SLS) or some of the newer machines that use metal powder with a plastic binder in what's more or less an FDM 3d printer, then sinter the printed parts in a kiln to produce metal parts.