Harper and Dylan want to share the responsibilities for their business as well as the tax advantages what business ownership structure will allow them to split the profits evenly while avoiding double taxation on their respective tax returns

An ideal business ownership structure for Harper and Dylan in this scenario would be a Limited Liability Company (LLC).

In an LLC, profits and losses can be split between the members (Harper and Dylan) in any way they choose, allowing them to evenly distribute the profits. Additionally, an LLC is a pass-through entity for tax purposes, meaning that the profits or losses of the business are passed through to the individual members' tax returns and are not subject to double taxation at the business level.

By forming an LLC, Harper and Dylan can share the responsibilities of running the business while also benefiting from the tax advantages of this ownership structure.