Build an Online Store

I am looking for Magento technical support to hire on monthly basis. He should be expert in Magento platform, and can develop and code for modification, can fix website errors, and knows customization and implementation of upgrades and plugins. This is an ongoing job per month, no specific task is appointed at this time, but he should be available to maintain, fix, and implement necessary functions to keep up with the site smooth operation and updates. Tasks will be appointed if needed, otherwise, it is his responsibility to watch the site and make sure it is running as it should. The site is an existing magento and fully loaded. I keep coming across some errors when adding plugins or updating some extensions. Some issues can get fixed by the hosting company if they are server related, however, other issues are beyond their expertise and mine, which will need the developer's expertise.