There is no typical split. But, in general, there should be one founder who owns a bit more that is the final tie-breaker. 

Additionally, founders usually bring a variety of different skills (technical and non-technical), connections, networks, intellectual property, track records, etc. in varying proportions that will affect the equity split. It is important that the founders clearly discuss this before embarking on the startup together, to minimize the chances of any disagreements down the road. Founder breakups are a common cause of startup failures.