Can rental property management be considered as self employment?

I have one rental property that I solely manage. Can I consider it as self employment so that I can open Individual 401k fund from that employment?  If I open LLC and be the sole owner, does it help? I want to contribute to my 401k from that employment as an employer. I am already contributing to 401k from my work as an employee. I am hoping that if I contribute to 401k then I can reduce my tax liability.