New PPOR or IP

I am thinking of buying my first home and live in Adelaide and earn 50k a year.
Currently living at home with parents(smartest move you can make when saving for a deopist). I have 30k saved up.
Thinking of buying a $250k house as an IP about 20km from the city versus buying a PPOR on a piece of land i have a hold on right now. The land is 9 km from the city with 18m frontage and 405m2(18×22.5) for $180K.
i alrealdy have plans for a 4 bedroom, double garage home. All up it will be around $350k-$370.
If i build this new house the family will probably be moving into it hence the 4 bedrooms and my parents house which they own outright will be rented out.

If i go the IP path i get someone to help me pay for my house and get to own it sooner and hopefully invest in more IPs. I also get to claim the interest payments and depreciation from the IP each year so better cashflow and probably put in an offset account. But i do not get the first home owners grant worth $11k in SA.
If i build my own home i get a new house to live in but will take longer to have the funds to buy any IPs. I can not claim any interests or depreciation but do get the first home owners grant.

To complicate things even more my parents own their PPOR outright and have 2 IPs.
IP1 is worth $280K and have $60k left on a principle and interest loan.Rent is $270 pw.
IP2 is worth $320k and have $180k on a interest only loan. Rent is $280pw.
Combined rent from both properties is $550pw yet interest payments for both house is around $450pw. If i build the new house and rent out my parents house they will have an extra $380pw in rent.

My dad has recently retired as well and the IP1 is an old house with not a lot of derpreciation value so the best plan we have come up with so far is to build the new house and live in it. Rent out my parents PPOR, keep IP2 and sell IP1 to pay down my PPOR i am building. I then buy IP3 with my mum. I get a new house and an IP at the same time and live happily ever after.