Do they need to use your credentials as an Assessor? If so, there is no set amount. Some Assessors and Moderators do this at no fee, but sign a Service Level Agreement, that once the company obtains their accreditation that the assessments will be given to you, whereby you will charge accordingly. Then there are Assessors/Moderators that charge between R400-R1500 to use their credentials for accreditation – and once the provider is accredited the first batch of assessments are done free of charge.
When assisting a provider, you need to at least sign a confidentiality agreement, and make sure that they are aware that they may only use your credentials for that specific application, and that they may not distribute your information to any other party (very important).