Well, most of the questions you asked can be answered yes. They are considered nuisence trees, are affordable, and they will fill up your five acres.
The reason they are a nuisence is they sucker up and you start to get hundreds of little australian pines, everywhere. They are tough to get rid of if you ever wanted to eliminate them. Since you have five acres this problem might not be too bad. You can fill up the whole yard affordable. Buy one and have them spread everywhere. They arent like rabbits. You wont wake up one morning and you have thousands, but you will see growth after a few years. Sounds like a beautiful area. Good luck.
Darin
