How big is the house you are looking at? Cos the build guarantee won't always apply (well you will still get paid x amount per week they are late but don't expect the actual build to be on time. Lots are I hope yours is one.

When you get a construction load with periodic drawdowns you only pay repayments on the amount you have drawndown. If you want interest only repayments it may affect the type of loan you have to apply for depending on the lender.

We built our house while selling so had to do both lots of repayments at once, and it was when the variable rate was over 9%

It was hard. But no worse that when I was on mat leave and we were on a much lower income.
Still you need to work out the realisitc repayments and the lender or broker will help with this. Then you may need to make decisions like do you need internet etc if it comes down to that.