Substance use treatment; Treatment for co-occurring substance use plus either serious mental health illness in adults/serious emotional disturbance in children; Outpatient; Regular outpatient treatment; No formal relationship with prescribing entity; Does not treat alcohol use disorder; Accepts clients using MAT but prescribed elsewhere; Cognitive behavioral therapy; Motivational interviewing; Telemedicine/telehealth therapy; Private for-profit organization; State mental health department; Federal, or any government funding for substance use treatment programs; Medicaid; Private health insurance; Cash or self-payment; Adolescents; Adult men; Clients who have experienced sexual abuse; Clients who have experienced intimate partner violence, domestic violence; Comprehensive mental health assessment; Comprehensive substance use assessment; Screening for substance use; Screening for mental disorders; Aftercare/continuing care; Discharge Planning; Naloxone and overdose education; Individual counseling; Group counseling; Family counseling; Marital/couples counseling; Smoking not permitted; Children/adolescents; Female; Male; Vaping not permitted; Mental health services