The referral system is a multi-chain network that requires intense marketing and that bookie that offers such betting always gives a good percentage payment on each referral but again if your referees are not active you may not earn so much as most bookies do so to discourage cheating.
Or he will be creating a review site for which this referral will be used for users to register. Not sure really what he plans to do with referral system but if he is a content creator like blogger, it must be the reason for him asking this. Hard work but it must pay good if the review site ranks well.
Cheating on referral is hard to do. They do have tracker for which they tend to look at where the traffic is from. If admin sees it don't add up, your account will be disabled.