If you don't have a lease in place now you can give them notice.

The illegal in-law units/ADUs are somewhat common in the Bay Area - many people with paid off properties are collecting under the table rent money without reporting it to the IRS.

If it's two mortgages, how common is it for a bank to do two at once for a new investor?

The goal is to get off of the spreadsheet and move to a common sense, "what makes my life better?"

Get rid of the side with the tenant that needs the most work or seems like they would be a nuisance to you to have to live next to (30-60 day notice on their door when you close if they're month to month) - update it and get it ready to get market rent for when you plan to do another one a year to two years later. 

While reading these discussions, notice whether people who share their opinions are qualified to do so.

I sent him a text and email letting him know that if I do not hear from him by 10/31 that I would issue a 3 day notice to pay or vacate.

In Florida, you would serve them a 3-day notice, and usually, the lease has a provision in it where you can charge them double rent or something similar for a holdover tenant.

You could give notice of non-renewal to one or more of the tenants, renovate those units, and then incrementally increase the rent of the other tenants.

I already gave them a notice that I will not be renewing their lease with the previous landlord which thankfully ends on 10/16.