Monthly Maintenance of Word Press Site

I have a car website that is built on Wordpress using a Theme. Yoast has been installed and configured for the sites current content.

As this is a car sales site the vehicles are changing on a weekly basis, the site owners are able to add and remove the vehicles but support is needed for the back end and SEO work.

I am looking for somebody that is experienced in dealing with this type of work and who will charge realistic prices.

There will be around 15 cars per month added and each car listing has on Average 20 pictures, these need to have all relevant Yoast SEO details filled in.

All spec and manufacturer details will be added by the site owner

Some other advice is required and, and I would like all monthly maintenance required for the site such as those offered by companies such as WPbuffs