It would have to be completely in compliance with ADs and if you are going over 25sm from your base airport or doing any true charter work you need a Part 135 AOC and have to be in compliance with the Part 135 regs. You can get a single pilot operator certificate for one pilot and one plane. You also would need to comply with Part 136 which regulates air tours.
Things you would have to do are brief passengers on safety features of the aircraft and provide life jackets (if flying over water). You also need permission to fly over national parks.
136.37 A commercial air tour operator may not conduct commercial air tour
operations over a national park or tribal land except
(1) In accordance with this section;
(2) In accordance with conditions and limitations prescribed for that operator by the Administrator; and
(3) In accordance with any applicable air tour management plan for the park or tribal lands
(b) Application for operating authority. Before commencing commercial air tour operations over a national park or tribal lands, a commercial air tour operator shall apply to the Administrator for authority to conduct the operations over the park or tribal land
If you are approved you may be subject to a limited number of tours over the area.
If you are keeping it under Part 91, with in 25sm, you will need a letter of authorization from your FSDO.
Regulations for Part 91
§91.147 Passenger carrying flights for compensation or hire.
Each Operator conducting passenger-carrying flights for compensation or hire must meet the following requirements unless all flights are conducted under §91.146.
(a) For the purposes of this section and for drug and alcohol testing, Operator means any person conducting nonstop passenger-carrying flights in an airplane or helicopter for compensation or hire in accordance with §§119.1(e)(2), 135.1(a)(5), or 121.1(d), of this chapter that begin and end at the same airport and are conducted within a 25-statute mile radius of that airport.
(b) An Operator must comply with the safety provisions of Part 136, subpart A of this chapter, and apply for and receive a Letter of Authorization from the Flight Standards District Office nearest to its principal place of business.
(c) Each application for a Letter of Authorization must include the following information:
(1) Name of Operator, agent, and any d/b/a (doing-business-as) under which that Operator does business;
(2) Principal business address and mailing address;
(3) Principal place of business (if different from business address);
(4) Name of person responsible for management of the business;
(5) Name of person responsible for aircraft maintenance;
(6) Type of aircraft, registration number(s), and make/model/series; and
(7) An Antidrug and Alcohol Misuse Prevention Program registration.
(d) The Operator must register and implement its drug and alcohol testing programs in accordance with Part 120 of this chapter.
(e) The Operator must comply with the provisions of the Letter of Authorization received.
I would assume that the aircraft would have to comply with Part 91 requirements. If in doubt ask your local FSDO.
THIS IS NOT LEGAL ADVICE. I AM NOT A LAWYER NOR DO I WORK FOR THE FAA. THIS IS A PILOT’S INTERPRETATION OF THE FARs.