Am I the only freelancer who cared to write at least two paragraphs after reading your description? Well, if you want to make it easy with paypal on paying the therapist, we can create a simple script that sends a payment to him from the business main paypal account... the pro both sides would use paypal accounts (client, you, and therapist)... the cons therapist could be charged again the paypal fee... but if this is not a problem for you we can discuss it.
The other option we can try another provider, most of them provide PHP libraries for us developers, one Ive used is mollie payments, but not precisely for paying just receiving.
I'm around if you wanna further discuss!
Now, what I copy-paste about me:
I've been in a web agency as web developer (both front and back end, although I prefer the second). Before that I was a jr programmer in a stock-market related company that selled databases here in Mexico.
I'm an engineer btw. I'm fluent in English, German and native in Spanish.
I would love to collaborate with you, let me know!
Alex