Hi Manuel. While I have never structured partnerships between companies and DCA's, I have worked on many strategic alliances with govt agencies (or the like) and companies. Increasingly this is becoming more and more common. Which State are you in? It may be worth reaching out via your network to...
You can simply divide equally among the three companies or divide the fee based on usage. Count the volume of mail received for each company. Each individual company's share would be Individual Company divided by the Total.
You might be somewhat in trouble. You'll want to consult a lawyer, not to be adversarial, but rather to ensure you do things that are legal and are best from a tax-consequence perspective. You can't back-date option grants or stock grants, for example. There are recent scandals reinforcing tha...