Judge Rhys Rowlands warned Cross, of Llys Nanthgarw in Wrexham, that he should expect a prison sentence when he returns to court to be sentenced on 7 January.
The Crown Prosecution Service (CPS) said Cross sent the chemicals through the post between 9 August and 13 September 2024, receiving £100 from each of the four individuals.
When police searched Cross’ address in January 2025, officers discovered amounts of the chemical and other paraphernalia, the court heard.
Det Supt Chris Bell, from North Wales Police, said: “Cross took advantage and exploited his victims in their most desperate moments, profiting off their vulnerability and mental illnesses.
“This has been a highly complex and sensitive investigation over the past 10 months, and I want to acknowledge the courage of the witnesses who played an integral part in the investigation during such difficult circumstances.
“Safeguarding vulnerable individuals is a priority for us, and we continue to work closely with partner agencies to provide support and prevent harm wherever possible.”