That's a really good question.
If I wanted to rent out my little G-reg PA28 because I'm not using it much, the maintenance is clear. It is maintained under Part M to old 'public cat' standards.
But as far as the CAA is concerned, anyone who wants to 'borrow it' and pay me £1000 per hour for the privilege needs to have a share in the aircraft or in the group - min 5%.
If it happens to be a fellow club member who might want to use it for a quick trip somewhere, that is rental.
So, I think, is selling blocks of hours.
So how does that work within the CAA's regime, not noted for flexibility.