How to serve notice?

[Graeme Harris]

Hello, my wife and I are about to close on our first house hack and we’re about to inherit two renters that are on month to month leases that are way below market rent. We have to give a 30 day notice to one or both of them because we have to live in one of the units. One unit also needs some TLC. 
Two questions 

Do we evict one or both?
what’s the best way to give notice? and is it okay to give them more notice than 30 days?