Rental income is taxed under Case V schedule D.
The total rent received or receivable is assessed.
You are entitled to deduct expenses related to the property such as 75% of the mortgage interest if registered with the PRTB. Repairs, insurance, letting fees. Capital allowances are available on fixtures and fittings @ 12.5%.
So let's say your rent is €1,000 per month and you borrow €150k @ 5% allowable interest €5,625, insurance €300, letting fees €300, accountants fees €300.
Your assessable profit is €5,475. This is subject to tax on each partner PRSI and USC at 49.5% if your PAYE income exceeds €33,800.