What does "three of the apartment units on the ground floor" mean in this context? [closed]

My firm is interested in purchasing the building at 1210 Prince Street. Since this property has been on the market for almost five years, it has fallen into disrepair. Regal Properties is willing to invest what is necessary to update the building

In addition, we would like to convert three of the apartment units on the ground floor facing the street into space for businesses.

So this is the whole letter text I got from the textbook. According to the answer sheet, the bold part means 'three single storey apartments'. I thought 'apartment units on the ground floor' meant the group of rooms on the ground floor, not the entire building. Can anyone explain this part for me?

The answer key is correct: 'three of the apartment units on the ground floor' refers to 'three single storey apartments'. These single storey apartments are all located on the ground floor of the building (hence 'on the ground floor').

You are correct that 'three single storey apartments' does not refer to the entire building but, rather, the group of three apartments. There is nothing in the quote that implies anything about the whole building.

myacorn is correct

The operative word there is "units", what you would probably refer to as "flats". An apartment complex might consist of several apartment buildings, each of which would contain a number of apartment units.