Welcome @Vicky it’s great that you want to join our pet loving community and start a pet sitting lifestyle but we do have a minimum age limit of 21 which is company policy and nothing to do with the legal age of consent.
My advice would be to get as much pet care experience as you can, volunteer at a shelter, pet sit for family and friends so that when you are able to join you will have references showing you have experience, are reliable, responsible and the person an owner would be confident to trust with the full and complete care of their home and pets.
Always look on the responsibility from the pet owners point of view and talk to other home and pet owners about what they would look for in an in home pet sitter, remember you are asking owners to trust you completely with two possessions they value most in the world.
Thank you again for connecting with our community, it’s a great place to start … Good luck!