On average what kind of pay does a porter/detailer make at a dealership?

This Nissan dealership has been hiring for porters/detailers for quite a long time now off and on and today they posted an add for immediate openings so i am going to apply tomorrow. The only thing is i keep questioning why people are always leaving the job or why they keep needing porters/detailers unless they simply have no one applying for the job. What duties do they do? I think the porter and detailer are two seperate positions so if you could explain each please. Also average pay. Thanks.