Something iv done many times, I currently have 4 chastity slaves (1 in Norway)
Number one rule.. He provides the chastity yes, But you provide the padlock therefore he has no key access (get from any hardware store)
I charge for sessions and the only time I charge for remote services is when they want tasks inbetween. Lets face it, keeping a key in your jewellery box shouldn't be chargeable
The good thing about having them locked up properly is that it provides a regular income, as the only time they are permitted release is during your session. This work out to be more profitable then charging to be key holder
Also make sure then wash before device is locked on and on removal, and they have to pee sitting down
Any questions feel free to ask

Mistress Devon x