Hi,
This is unfortunate. Arguably, if you had hit an unlawfully parked car (likely to be one parked on a nature reserve) then there would be a strong likelihood that you could raise a defence against any allegation of negligence, particularly on the grounds of contributory negligence.
However, we understand that you've hit the lawfully parked car. We also assume that you're not able to make a claim with your insurer.
Accordingly, the owner of the car parked lawfully on the street will not have been negligent (by contribution or otherwise) in any way and is likely to sue you for negligence on the grounds of failing to keep a proper lookout.
Whilst you could seek to join or pursue the third party car parked on the nature reserve, this would be complex in practice (given that you would need to perform a REVS search to find their details, lodge the appropriate claim / court documentation etc.) and there is certainly no guarantee that a (presumably) Magistrate would be persuaded by your line of argument.
In cases like this where you are at fault and aren't insured, I recommend speaking with a community legal service - they are likely to advise you to have a summary judgement entered against you (by not filing a defence - if a valid claim is instigated against you in a Magistrates Court) and then if that judgement is enforced by the car owner, you will likely be able to enter into a Court ordered payment at a rate that you can afford to pay the car damage off over time (i.e. this will avoid paying for the damage in one lump sum - which is often hard). You may even be able to negotiate a payment plan with the vehicle owner outside of court if they are amenable to this.
Laws may be different in NSW and so I would seek community advice in that jurisdiction to clarify the above.
Hope that this helped in some way.