Substance use treatment; Outpatient; Outpatient methadone/buprenorphine or naltrexone treatment; Methadone used in Treatment; Does not treat alcohol use disorder; Federally-certified Opioid Treatment Program; Methadone maintenance for predetermined time; Methadone; Substance use disorder counseling; Private for-profit organization; State Substance use treatment agency; State department of health; Cash or self-payment; Comprehensive substance use assessment; Outreach to persons in the community; Screening for substance use; Drug or alcohol urine screening; TB screening; Discharge Planning; Outcome follow-up after discharge; Opioids detoxification; HIV or AIDS education, counseling, or support; Hepatitis education, counseling, or support; Health education services other than HIV/AIDS or hepatitis; Substance use disorder education; Individual counseling; Group counseling; Smoking not permitted; Adults; Young adults; Female; Male; Opioid use disorder clients only; Case management service; Social skills development