Purchasing costs - not deductible whether ppor nor IP. So a non issue at this point. They do form part of the CGT calculations when you sell, though.
Borrowing costs - these are deductible over 5 years, ie 20% of them per year. So, if it was ppor for 2 yrs and IP for 3 yrs, then I think it'd be fair to deduct 0 in year 1 and 2, and 20% each of years 3, 4 and 5.
However, I'm not an accountant. Check with your own to be sure.