ERP support for an organization, implementing a new ERP system is always a major consideration. Even with a mature, installed ERP, support is still critical throughout its lifecycle. In addition to the expected internal IT support, companies necessarily rely on support from the supplier for fixes, updates and enhancements and may also rely on other resources for other kinds of ERP support.
When planning your need for ERP support, staffing ratios and other rules of thumb might be helpful, but it really comes down to the amount of in-house support there is and how reliant you will be on outside support. An internal staff for ERP support may be easier to manage, as it will most likely be on-site. This, however, does mean expenses for training, overhead and sometimes even higher wages.