You can modify the system to be able to purchase Resource.
is it an item or a service? The intrinsic difference between the two is that an item would normally consist of you wanting to keep an eye on and manage your inventory levels.
A service is something this is not of a define quantited, so they operate difference.
what are you trying to acheive?
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Had you try explore the possibility of non stock item? However I still think it's good to use G/L for purchase service. I wonder why you don't want to do that way.