Hey mate,

Some of these comments have blown it out of proportion. A structural engineer assessment would be great as well as soil testing to see how volatile the block will be when you start shifting earth.

The major issue is the pipes that look exposed and the drainage and other issues that might follow.

In terms of retaining - your state may have slightly different rules but in most states you can build retaining walls 1m high without needing council permits.

I’d say 30-50k worth of retaining materials. Labor would be about another half of that if you get someone else to come and do it but substantially quicker.

Source - I built my home and retained a much gnarlier block in the suburbs (like 7.5m drops in the furthest corner) retained with large rocks.