I am not sure how that would work have only ever claimed v paye income ... but if you have paye my account, logon to the site and submit a form 12 for 2017 with the amounts. You might get lucky... My folks claimed for it and they had state pension so hadnt even paid any tax in the year.
If it is paid out it would be 300 euros refund based on 1500 at 20pc.
If the expenses fit the categories [broken link removed]you will get a credit of 20% of the expenses. It doesn't matter what kind of income you have but the relief is only against income tax, not USC or PRSI.
When I submit a form 12 for rental I also include the Med 1 form separately but I'm pretty sure that there is some section for medicals on the form 12 itself.