What is the industry standard (or your opinion) for profit splitting with a cosigner?

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Person A bought a house for $200,000, but needed additional credit to purchase. 

Person B, cosigned (and was on the deed) for said house. 

Only Person A lived in and made payments on the house (on time every month so there was no damage to Person B’s credit) for 5 years. 

Person A is moving and the house is being sold. The house is selling for $300,000, which means there is a large profit being made. No prior contract arrangements were made detailing profit split.

What do you think would be fair profit split for this situation? Thank you!