Community access and participation for people with intellectual and developmental disabilities (IDD) depends in part on competent, committed direct support professionals (DSPs) who support people with IDD. With knowledge of the person's communication preferences, support needs, and environments where supports are provided, DSPs can support their inclusion and independence by accounting for people's self-determination, goals, and choices. However, providing such support requires advanced skill, training, and supervision beyond what is typically provided to DSPs. DSPs are considered entry-level workers and usually have little access to training or professional development opportunities. The mismatch of training and support for the workforce has led to a systemic crisis due to a critical shortage of reliable workers that needs to be addressed with feasible solutions. The purpose of this multiple-study dissertation was to use empirical methods to explore professional development pathways that may support DSPs to obtain skills needed on the job and which hold the potential to encourage staff to stay in the workforce over time. Study 1 is a phenomenological analysis of DSP interviews designed to identify what was common and necessary about DSPs' experiences in voluntary employer-sponsored credential(s) programs in one state that include competency-based training and a commensurate wage increase or bonus upon completion. Study 2 is a systematic literature review on the Self-Determined Career Design Model (SDCDM), which was originally developed to be implemented in vocational rehabilitation to support job seekers with disabilities to explore, obtain, and maintain employment by having structured opportunities to practice self-determination by working toward a career-related goal. The SDCDM has been adapted for multiple populations, settings, and needs since it was first developed. This systematic literature review focuses on with whom and where the SDCDM has been implemented, its effects and how effects were measured, and adaptations to the SDCDM when it has been implemented in different circumstances. Findings from these studies will be used to inform an ongoing line of research aimed at improving training and professional development for DSPs. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]