Whenever a petition is filed with the inspector charging that any dwelling is unfit for human habitation or whenever it appears to the inspector (on his own motion) that any dwelling is unfit for human habitation, the inspector shall, if his preliminary investigation discloses a basis for such charges, issue and cause to be served upon the owner of and parties having an interest in such dwelling including lien holders and tenants, if any, as the same may be determined by reasonable diligence, a complaint setting forth the charges, The complaint shall contain a notice that a hearing will be held before the inspector (or his designated agent) at a place within the County in which the property is located therein fixed not less than 10 days nor more than 30 days after the serving of such complaint; that the owner and parties in interest shall be given a right to file an answer and to give testimony at the place and time fixed in the complaint; and that the rules of evidence prevailing in courts of law or equity shall not be controlling in hearings before the inspector.