The best way to manage this aspect of being a consultant is to sit down and thrash out a high quality business plan. The worst kind of plans are created in just a couple of hours, but if you are committed to making your whole consultancy thing happen, you will put the time in to create a quality, detailed business plan that you can show to investors and clients.
If it is carefully created, it should have all the elements of the classic business plan model, and this should be clear to you or any other stakeholders as soon as they see it. Take the time to ensure that the executive summary is compelling, and that all the financials are in place, this way you can guarantee that people will take it seriously.
It is also vitally important that you have someone else take a look at the plan before you crystallise it for good, while all plans should be fluid, this does not always work out to be the case, so having someone else looking at the plan in principle should allow for some confidence in your plan and how it will work out for you.
Whatever you do, don’t avoid creating a business plan. It is essential if you are to survive, and this is a major aspect of running your consultancy.