All your income MUST be deposited into one single bank account.

I'd like to next buy a duplex/triplex and step foot through the multi-family investing door while continuing to do single-family house flips.  

According the the founder of TechVestor, they find that larger 4-7 bedrooms perform better when it comes to a standard single family. https://www.linkedin.com/posts/taylor-jones-38997154_average...

If you do catch them, pressing charges and getting police to do anything is next to impossible. 

Having someone hold me accountable makes me strive for more and progress over perfection every single day.

Typically, 20+ will be in the commercial brokers, and from here there is no real central database of listing, like the MLS is for single family and smaller multis.

An LLC wholly owned by a single person is disregarded for federal tax purposes, so as far as the IRS is concerned you took an asset out of one pocket and put it into your other pocket.

I just have seen more success with single family in my opinion.

How would you go about charging utilities to tenants? 

This is a surrender charge.