Co-Founder of Eurobrands Consulting (a Market Entry & Expansion firm for the Indian market). I have been consulting international companies entering the Indian market for the past 10 years. Studied International Economics and Marketing in Austria and UK and worked for a global KPO in India and Trade Institutions in Europe.
I would set up a simple referral fee agreement.
This could be 15% on the overall billing paid out the moment the client pays the market entry consultancy.
You may want to include a clause that all recurring business should also attract a referral fee. Consulting assignments with new clients normally start small and then grow bigger over time.