I am forming a team/business partner to start on real estate investing, and I want to ask if we need to get some kind of formal business licence such as an LLC...or we can just do it in personal/individual level? 

I took my time to submit a formal written offer with proof of funds.

and I give them formal 3 day notice. 

But I have changed my formal dining room and sitting room into bedrooms. 

There are formalities that have to be followed if you create an LLC and if you don't follow them properly, having an LLC is pointless.

If they have been there for sometime and are paying the rent, I wouldn't bother with doing formal tenant application & screening.

And if/when I do - should that just be a face to face conversation or a formal notice that they were instructed to move their car?

I definitely need to create a spreadsheet that more formal looking as well.

I wanted to open a formal complaint to the Maryland Licensing office which is where we live, but I am not sure where to begin.

@Micah Carter I didn't have any formal home repair knowledge but I have always been one who likes working with my hands and figuring things out.