But the common narration that "I'll just do a few flips/wholesales and boom I'll have enough money for a down payment for that xx unit building" is so much more complicated than advertised. 

While they can be developed in some areas, don't assume this strategy is common place and make sure to do some solid due diligence before purchasing.

It was definitely more common at one time to have sinks in bedrooms.

My lease says no more than 8 days every month because it's common for them to have someone over every weekend.You don't need to prove it.

We just found about it and I am little frustrated because now I have to coordinate times with the tenants.Is this a common practice for refinancing?

Beyond that, a lot of life is just common sense.

It's common to use properties in your portfolio as stepping stones and trading them out after a period of time utilizing great tools such as the 1031 exchange.

Appraisal demand is quite high at this moment, and rush fees and higher fees for more rural areas are common practice.   

I have read that turnover is much more common in multi units than in SFR properties, and the reasons given make sense.

A common way to do what you're looking to do is to have a different bank account for each LLC and set that up in your one account in the landlord app –– so that the money for each property automatically flows to the appropriate LLC.