95 camry a/c

It can leak whether on the low or high side running or not

Leakages can occur at any part of the system and for seals, they would tend to leak faster when not in use and parked for extended period of time.

what is the cheapest and easiest way to find a leak. when i turn on the a/c on full blast, i hear a leaking sound.

Usually you would not hear any leakage noise. If yes, the leak would be very bad and the system would not hold any pressure.

There are dyes available for testing leaks.