How to deal with URLs in self service applications

Hi everyone,

i am developing our service to make a shift into the self-service field.

There our users can create their own test application with an URL. 

Here the question:

How do you deal with the domain availability? 

Any cases of fraud etc. when opening this up and letting everyone create a custom one? How do you deal with users that “block” a different company name for their own application? 

Would love to get some feedback and best practices!

Thanks!

Dominik