This might be a dumb question but I want to know if I can use the Ground and any of the pins of the Arduino Nano as signals for a project. I want to have a single ground and if moisture touches a pin wire it sees voltage? I am looking at using 5 pins for this project to know where the moisture is. Please note that I do not want to buy any add-ons just wiring it.
I want to know if I can use the Ground and any of the pins of the Arduino Nano as signals for a project
No.
I want to have a single ground and if moisture touches a pin wire it sees voltage?
Nothing wrong with the single ground but what do you mean by “moisture touches a pin wire“? That is a very vague statement.
If you mean there is electrical connection between the pin and ground caused by condensed water bridging the gap, then you will read a signal providing you have a pull up resistor on the input pin and sufficient moisture is present to act as a resistor to pull the input to below the zero threshold for your board. This threshold voltage depends on the voltage powering the board which for a nano can be 3V3 or 5V.
However while you might get something to work, this sort of thing in not very reliable.
When I say moisture I mean water to bridge the gap between the two wires. Wires would be at ground level and once the circuit is completed it should notice the change.
Try a 1M pull up resistor on the input.