One thing lawyers in private practice grumble about universally is that their clients seem to not appreciate the value represented by their work. I have heard it over and over: “all they gripe about is the billing rate! Don’t they know what it took for me to gain the ability to handle their legal matter?”
Well here is a bit of good news: any nonlawyer who has tried to handle their own legal matter WILL appreciate your value! Just because the prospective client wants limited scope representation does not mean they do not think you are worth your fees. It generally means they have, well, limited means.
Rather than try to finance their matter and take the risk of nonpayment on yourself, break the representation down into discreet phases and tasks and see what you can do for a modest, set fee. Paid in advance, of course.
Chances are high that the “do it yourselfer” who has turned to you for help will be much more understanding about that fee than someone who wants you to handle the entire matter for some mysterious (from their perspective) cost to be determined as you go along.
And who knows? The client of your limited scope practice may come into an improved financial situation and be able–and quite willing–to pay you for full scope representation!