young family guy first home buy need help

Hi guys im very new to this site, I was advised to get some feedback off here before I made any decisions in relation to buying my first home…

The situation….

Im young married 2 kids, 6yo and a 4 month old. I have a government job and my wife works full time.

We live in a very small 3 bed place single garage with no garden shed so we have stuff everywhere. We thought about renting a bigger place but the average rent around my area is 400 + for something with more space and that just seems like so much to pay in rent. So we looked into buying, we like the area we live in so we wanted something close. We also have some current car debt so paying 400 rent plus debt repayments we were looking at $600 per week anyway. We don’t have a lot of savings but the reason we looked into buying was that we notice a billboard on the side of the highway saying No deposit house and land building boost $10,000.

This prompted us to enquire straight away as I have the real estate up my chuff to sign the lease for another year so I wanted to check out my options.
We went to a stockland estate called Ormeau Ridge at Ormeau. It is in stage 4 of a 25 stage estate. We spoke to a few builders and we found the best value for money was 23sq place which had 4 beds + Media + activity area + alfresco and double lock up on a block 448sqm for $380,000 this was a fix price including driveway, turf and fencing the only thing it didn’t include was curtains and turf to rear. I thought that was pretty good considering some of the pre existing homes I have seen around for the same price were rubbish.

We spoke to a finance guy and he told us that it was possible for us to do this if we had my wifes mother go Guarantor and then in a few years if we had some equity in the house the guarantee would be released on the mother in-laws house.

My reasoning behind this was that I had thought that the decline in the market was pretty close to levelling out because the average rent is pretty close to a tenth of the average house price.
So I thought that if I bought a house in the early stages of a development that by the time the development was finished that I would have gained the small amount of equity to release the guarantee on the mothers house.

My father works the stock market and has advised me that houses are going to plummit. I have since agreed not to buy until he says its ok but he has told me to ask for people opinions on here so if you can help that would be much appreciated.

Thank you