We converted the first floor into an airbnb with a separate entrance, and the top floor is our living space that we share with a roommate - we're not necessarily cash flowing every month, but our mortgage is usually at least covered. 

Large apartments, high ceilings, spacious entrances.

It fronts to a state highway, and there are guidelines that control the width of the entrance, the paving material used, and the drainage.

You don't need to go overboard, just a camera at each parking entrance/exit, the leasing office, and 1-2 other important places around the property. 

For instance, I bought a place that is a fantastic rental (cashflows $1,000/mo), but it has a staircase awkwardly placed right inside the main entrance.

There is only one maybe two entrances to the community and over 200 miles of poorly planned streets. the place is a labyrinth.

It's usually well posted at the entrance of a subdivision, and the residents do not take kindly to folks ignoring the rule.

(near to the garage entrance).

If it doesn't have the required things to be a dwelling on its own such as a kitchen or its own entrance then you'd be renting a room in a rooming house.

I would like to get advise on if any disadvantages or things to beware of if I am buying property where 1 bedroom and bathroom is created separately on lot with separate entrance ‘without permit’ .