as an architect
we wouldn't charge you for an initial visit/assessment but would advise without prejudice or reward based on the suitability of the building for your purpose, advice on change of use, planning, etc, etc. and would hope you'd appoint us to take job forward. would also advise on need for other consultants ie structural survey/comments if required.
if you wanted something written or report for finance/business case then a fee would/might come into it.
although as we're all cutting each others throats at the moment you will get lots of differing advice and as always you end up getting what you pay for. my advice would be to approach architects with experience in the type of project you're looking at and then see what they say, most will do a no obligation first assessment.