If they are being honest, every landlord will tell you they have had days of despair.
However, if you run it like a business you can do well.
If you don’t run it as a business; don’t enforce your rules; don’t know the laws; let problems affect you personally instead of approaching them logically; or don’t calculate for expected costs, you will fail.
The best way to find the path to success is to actively participate in local landlord groups.