Limit on custom subdomain?

Hi there, I had a question regarding the creation of subdomains from my domain name. I essentially want to create separate apps for clients. I already have a domain connected to my main website on softr let’s say myapp.co
I want for each client of mines to have their profile on a separate subdomain. Example: client1.myapp.co, client2.myapp.co etc. Is it free to create unlimited apps using my domain as a subdomain? Or do I have to upgrade to pro and purchase custom domains at I believe 13/mo? For every app I make for my clients? How does pricing work in regards to custom subdomains? Essentially the same way we can create unlimited apps on the .softr.io subdomain could it be done with a custom domain?

This article might solve your issue: Add a Custom Subdomain to Your App – Softr Help Docs