What exactly is it you need?
For example, an accountant is best place to advise on the finances, forecasts, projections, deciding if finance raising is necessary, book-keeping, creating invoices, time charging systems, debt collection, setting up business bank accounts, etc.
A solicitor is best place for drafting legal contracts/terms of business between yourself and your customers and also for considering aspects of employing staff or contractors, evaluating risk, etc.
A decent insurance broker would talk you through the different types of insurance.
A designer would talk you through developing a website, branding etc.
No individual "guru" would know all this in enough detail - the best they'd do is to have generic conversations with you and then sign post you to these people, charging you a small fortune along the way for probably telling you what you already know or what could easily be researched via Google!