NEVER EVER combine your clients in one database. Also EACH USER should be held accountable for access in order to protect the Audit trail along with HIPAA compliance. Even as a billing company owner, if you have others access a client's database they must have their OWN login (secure). The audit trail MUST be protected.
If you are in NY but you bill for a provider in another state that does not prohibit providers from entering into a contract that is considered fee-splitting you would be ok. Remember it's not the billing company that is libel it's the provider. However I still maintain that billing a percentage is still an enticement to fraud and abuse and the billing company NEVER receives fair compensation for their hard work. I just don't believe in % based billing at all anymore.
As for credentialing. I never include that in my billing contract. It's a separate contract (consulting) and I also go much further than just plain credentialing. There are two tiers to credentialing and depending on how far you go with it I would go based on an hourly fee if your doing ALL of the work (Fee schedule analysis, adjustment analysis, contract review, negotiations, etc) or a flat fee if your only service is to just get them in network.
As for NY and fee-splitting.... You won't lose providers if you explain it properly. Explain that it's you that is protecting THEM. They are the ones that would end up in trouble, not you. It is NOT illegal for YOU to charge a %. It is illegal for them (providers) to enter into a contract that fee-splits. If you explain it like that, your golden. If you are a PMRNC member we have some great resources on fee-splitting in our members only area. I think it would be impossible to lose a client for trying to protect them. It's also been a great marketing tool for me since there are so many billing company's in NY that ignore this law. Again, remember it's NOT the billing company that's acting illegally, it's the provider signing the contract.