I agree with blueisallineed, if you aren't prepared for it, then you should release it. Once you get everything ready for them, then you can buy one.

Green tree frogs can be $20 to around $40 in Australia.

When you said 'you wasted your money because you can catch it for free' its not wasting if its going to good use.

And anyways, wild caught frogs life span is much shorter than captive bread frogs.