There are three ways in which people can collaborate on pet-related things: by either group buying pets or pet-related items (such as foods and toys) or pet services (such as pet walking), taking turns pet-sitting, or by time-sharing a pet.

When it comes to group buying pet products or services, the considerations are similar to the general rules of group buying or service group buying. For more information, you can read General Consideration or Service Consideration
And when it comes to cooperation, such as taking turns pet-sitting, the considerations are similar to the cooperation consideration. For more information, you can read Cooperation Consideration

There are many reasons why people choose to share a pet, including financial constraints, work or travel schedules, or simply not wanting to commit to a full-time pet. Sharing a pet can also provide companionship, reduce stress and anxiety, and promote a healthier lifestyle.

Pets commonly shared among people are dogs, cats, birds, rabbits, and reptiles. While sharing fish is possible, it's essential to consider the potential negative impact on their well-being due to the stress of moving them frequently.

However, sharing a pet between friends also requires careful consideration and planning:

1. Compatibility:
   The first and most important consideration when sharing a pet between friends is compatibility. It is important to ensure that the pet is compatible with all friends' lifestyles, personalities, and living arrangements. This will help to ensure that the pet is happy and healthy in all environments.

2. Care and Responsibility:
   Another important consideration when sharing a pet between friends is care and responsibility. It is important to establish clear guidelines for who will be responsible for providing food, water, exercise, and veterinary care. This includes discussing who will pay for the pet's expenses and how decisions regarding the pet's health and well-being will be made.

3. Communication:
   Communication is key when sharing a pet between friends. It is important to establish open and honest communication channels to ensure that all friends are on the same page regarding the pet's needs and well-being. This includes discussing any concerns or issues that arise and working together to find solutions that are in the best interest of the pet.

4. Emotional Attachment:
   The emotional attachment that can develop between the pet and its caretakers. It's essential to have a plan in place for how the pet will be cared for in the event that one of the caretakers can no longer participate in the arrangement. This can be difficult and emotional, but it's important to prioritize the pet's well-being above all else.

5. Schedule and Time:
   Sharing a pet between friends also requires careful scheduling and time management. It is important to establish a schedule for when the pet will be with each friend, and to ensure that all friends have adequate time to care for the pet. This may involve coordinating schedules, creating a shared calendar, or establishing a routine that works for everyone involved.

6. Legal Considerations:
   Finally, it is important to consider the legal implications of sharing a pet between friends. This may include discussing ownership and custody arrangements, ensuring that the pet is properly licensed and registered, and establishing clear guidelines for what will happen to the pet in the event that the sharing arrangement is no longer feasible.