Selinux cannot be the problem with SSH, if you haven't changed the SSH server listening port. Selinux has sane defaults for SSH, much less for other application… one of the bigger concern in learning RHEL/CentOS is not how to make everything running, but how to run it with Selinux ENFORCED.
Of course, never disable Selinux. Never.
It's maybe the most valuable security feature on the whole Linux ecosystem.