SOLO 401K for Real Estate LLC

Good afternoon,

I have some money saved up from having my own business which is a Restaurant. I would like to start saving for my retirement but not sure where to start. I heard about a SOLO 401K but in my restaurant I have full time employees, so I don’t think I would qualify thru that business. Now ,I have a Multi Use property that is generating around $8,000 a month in rents. That property is under an LLC, can I use the income from that property to pay myself and open a SOLO 401K? If so how would I set it up? The current members of the multi use property are my wife and I. Should I add Both of us to payroll or can it just be me?

Thank you so much for taking time to answer my questions.