Freelancers largely live and die by referrals. Their future work tends to come from people who heard good things about their efforts from previous clients. Most people understand this concept and, unfortunately, there are more than a handful who attempt to exploit it.
The conversation between a would-be client and a freelancer under this circumstance tends to go along the lines of the following:
Hey, I really want your help but can’t really pay. I’ll tell you what: If you do me this favor, I’ll be sure to put in a good word for you with some people I know that want similar things. You’ll have a new batch of clients and easily make back what you would have made with me. It will be win-win!
When it comes to prospects and clients, as far as freelancing goes, one rule of thumb to keep in mind is this: “Birds of a feather, flock together“. Individuals from a given industry/organization/income bracket/etc tend to have friends and associates from the very same.
While this is hardly a hard-and-fast rule, you should understand that if you are approached by someone who is interested in your work, but is unable to properly compensate you for it, there is a very good chance that anyone they could refer you to would be in no position to do you a better justice for a similar output of your time and trouble.
In short: Promises like these tend to be wild goose chases and should rarely, if ever, be encouraged.
However, for the sake of argument, lets say that you wanted to give this individual or organization a fair enough chance to put-their-money-where-their-proverbial-mouth is. In that case, I would suggest you begin your response with five simple, but nonetheless timeless, words:
I want it in writing
Now this is where the “payment terms” portion of your contract will come in (You do use contracts for your projects, right? RIGHT?!?!?): You and your prospect would agree on what would be a fair dollar amount value of your work. You would then take this dollar amount, put a premium on it, and tell the prospective party that, in exchange for your performance on the project they want executed, that they would be legally bound to generate one or more leads for you that would net you compensation that is at least equal to, if not greater than, the premium quote.
To make sure they don’t drag their feet, you state an enforceable timetable for your prospect to come up with these leads in (the exact lead time will depend on the type of work you do and how many leads are being promised). Finally: Make it very clear that a failure to execute on this part will be considered a breach of contract and grounds for collections/legal proceedings, just as it would be if they didn’t fully pay you outright.
At this point, the prospect party will likely bristly and try to get you to bend on this. The following stick-to-your-guns response, or something along its lines, will either shut them up and turn them away or shut them up and get them looking for a pen:
Listen: This will protect both of us and ensure that we don’t waste each others time. It will reasonably assure you that I can and will do what I say I can do for you and it will reasonably assure me that you can and will do what you say you can do for me….
…unless you DON’T think that you can actually do it, DO YOU? O_O