Per diem residential placements require payment to a provider for services rendered according to daily cost. Many State/local human service agencies use these resources to provide a continuum of care for offender treatment. This article presents a method for projecting cost and use via a seasonal/policy sensitive simulation model for per diem placements. It includes historic data for the Nation and for the State of Maryland. The article claims that this projection model has applications across various levels of care to other human service agencies and both public and private providers. The performance budget paradigm is an efficient and effective blend of accounting and program planning. Private domains could use the paper's various concepts to project revenues and Average Daily Populations (ADPs), whereas public domains could use the concepts to project costs and ADPs. Computer spreadsheet files for both the performance budget computations and projection model are available upon request. References, appendix