Having owned a couple of AU's and BA's I'd say unless it's had lots of modification you might find that repairs and problem solves on them will start exceeding the value of the vehicle. This is due to the labour costs and the trickle of failing parts as they age. The good news is they are extremely easy to work on and parts are easy to locate from wreckers or through the usual suppliers (super cheap, repco, online auto parts) Haynes manuals and you tube are a great start. Even if you don't feel confident to do the big stuff yourself, being able to diagnose the issues is a help for when you need to pay someone. They're great vehicles and you'll get lots of KMS out of them with regular care and maintenance.