What a site will realistically support, established early enough to inform the offer rather than explain the loss.
What can be consented on the site, rather than what could physically be built on it. Those are different numbers, and the gap between them is where most development money is lost.
A study tests the realistic quantum against local policy and the site's actual constraints — access, levels, daylight, amenity, parking, designations — and reports it as a figure you can put into an appraisal, with the reasoning shown.
Before the site is bought, while walking away is still an option. A feasibility study is the cheapest work on a project and the only one that can change whether the project happens at all.
For a site already under offer subject to planning, it also sets the strategy for the application that follows, so the work is not repeated.
Indicative layouts, a capacity figure, and a written appraisal setting out what drives it and where the risks sit. Enough to make an acquisition decision, and enough to brief the planning application if the answer is yes.
Describe what you have in mind and we will say plainly whether this is the right service for it, and what it would involve.