Can I please get an honest opinion about building a double storey house?

Sam, build the home you want if your long term view is to live in it. You shouldn't have too much problem renting it out. As the landlord, you have final say on prospective tenants, so engage a good agent and screen them well. When it is time for you to move in, give the home a complete freshen up, paint the walls, change carpet if you have to etc. It should still feel like a new home then. Good luck.

There isn't many two story houses in the area so i think it would rent out fairly easy if you ask a realistic price. You won't get as much rental return as if you built in say point cook