What is a residential unit for 54f considerations

In reference to Long term Capital Gain/ Sec 54, What  a residential unit mean? 

1) One room - Kitchen - bath totaling  200Sqft on 1500 sqft land with electricity connection.

2) One room Kitchen - bath totaling  200Sqft on 2400 sqft land with electricity connection.

Will 1) and 2) qualify as ` a residential unit` ?  ( if both of  them generated rental incom?) 

Thanks