There is a real Corporex LLC but it is not at all associated with mystery shopping. There is a current scam using the Corporex name that is sending out fraudulent checks, usually for $2830. This is not legit. Do not deposit the checks. Rather turn them and all paperwork that came with them to authorities. Be aware that you will NEVER be sent money up front for your first work with any legitimate company and even when you are very experienced with a particular company it is very very rare that you can negotiate money up front to help with any costs of the shop. But NEVER NEVER NEVER will you be paid your fee before you perform.