@Ryan Mortimer You should create an LLC partnership for the two of you for the renovation project. Keep the buying/selling totally separate. When you sell, whatever capital was invested by each party is reimbursed. The profit should be split based upon whatever agreement the two of you come up with.
It would be unfair for you to put in the majority of sweat equity as well as the training involved to have a 50% profit split. The agent that you partner with should understand that.
Keep the buying and selling totally separate from the refurbishment. The commission on the selling side should be paid out by the LLC before any profit sharing. So, the agent may earn a profit getting a selling commission, but the agent is also responsible for marketing and other fees. It is the agent's responsibility to make sure all parts of the selling process are taken care of properly. Same goes when acting as the buyer's agent.
This is three separate and distinct business transactions. not one. The agent's buying/selling activities have nothing to do with the property renovation project, and must be treated that way except to inform the public of the agent's personal interest in the property.