This is what the Revenue say:
Rent-a-Room Relief
Where a room (or rooms) in a person’s sole or main residence is (are) let as residential accommodation, gross annual rental income of up to €7,620 is exempt from tax. Relief in respect of mortgage interest relief is not affected. The relevant Capital Gains Tax/Stamp Duty provisions are also not affected. For more information see Leaflet IT 70.
[You need to note that the 'rental' includes ALL payments made to you. For example if the lads pay €3,000 for the phone, tv, internet, laundry, massage etc.. and €5,000 in straight rent..the total is €8,000 and is outside the relief.
So: just be careful on how these services are paid for ..as when the garage goes up ..you might easily slip over the limit.]