Barring some remarkable and exceptional circumstances, I’d agree with the sentiment expressed by Bob K.
There is a CD (more than one?) where it was comprehensively found that a clmt renting out a single property was not self-employed in such a situation. The clmt had argued that he WAS self-employed and, in turn, the property was a business asset (hence not capital for benefit purposes). In addition, a national insurance exemption certificate was found to be NOT conclusive of the self-employed status of the clmt.
The CD in question is [b:3494195f87]R(FC) 02/92 (aka CFC/0015/1990)[/b:3494195f87]. I doubt there would be any material difference in findings for HB/CTB purposes etc.
Just wondering: How many properties does it need to be before you are self-employed?