Hi, I too used to work in care & have also had experience with penile catheters. I would absolutely not get involved with that outside of a medical environment. The penis isn't meant to have things inserted into it, I would be terrified of damageing the soft tissue inside & causing bleeding or infection. I think your absolutely wise to be concerned! It sounds like this guys would be better seeing a medical fetish expert, Mistressis with white rooms & all that. Most of them seem to be ex nurses & have all the sanitized equipment & knowledge + experience. If you want to offer that kind of service I would look up an Mistress who may advise you or offer training?
Your call but good luck, Harlow x