You're killing me here man.This thread is about a proposal that would discourage corporate landlords from raising rent by more than 5%/yr by reducing their federal tax breaks if they do it.It's not my fault if you didn't read the actual proposal nor the other half of the OP that specifically mentioned the tax breaks being what is tied to the rent increase limit.You can't separate them. 

The mobile home was sold separate from the land.

Is it recommended to have a separate checking account for this or we can get it transferred to our personal checking account?  

Of course if laws were broken IE allowing non accredits in that should not have been.. allowing unlicensed 3rd parties to raise money etc etc.. those are separate issues as well.

Or do most larger investors keep a separate credit card and checking account for each LLC rental?

Especially if the house can be subdivided from the storage and sold and managed separately. 

@Zehua ZhouYour LLC should be a completely separate entity from you.

Electric Meters: I doubt the even if the ADU is a separate structure they have a separate electric meter as they were mainly used for guests.

I'm considering setting up my LLCs in Series and one thing I'm interested in doing is getting separate credit cards for each additional series.

You may want a separate spreadsheet for personal tracking, but that depends on what you are trying to accomplish.