Stable server provider ...
 

Which server is better to sign up with black.host or hostsailor.com?
What should I do?

I think that your choice will depend on the server configuration and your budget.
In October 2023 I signed up for the dedicated server from neironvps.com.
I have to say that I'm happy enough with their services.

I can advise you to compare all web hosting services, as it is a top priority for your new web host business to be well-provided with all necessary tools. Take a look at these server hosts:
1) Gigapros.com
2) GTHost.com
Really great services! It's unbelievable to get such great service at such a cheap price.