Has he considered prepaid credit cards? I'd imagine with that kind of transaction volume he could get a very good rate/break on the fees to load the cards up front. They'd be managed as separate "accounts" so if Susie is in Argentina and spends $10k it won't raise any red flags for Joey in Amsterdam's account. If they're generating that kind of activity regularly, I would imagine he is paying most or all of the balance each month to avoid huge interest charges. I bet he could even find a bank willing to automatically draft the transfer of money from checking to the prepaid Visas on a monthly basis, with that kind of volume.