I found a White’s bullseye 2 for $30 on letgo. Should I go for it?
That depends. I know you are on a tight budget. Do you have to pay shipping or taxes or can you pick it up locally and maybe get the seller down to $25 or less which is basically half price. Is it in good shape?
So there are two main types of pinpointers. One give a continuos beep/vibrates when you get close to the object. In the case of the Bullseye II depending on where you are able to set its calibration, you will get a continuous beep between 1.5" and 1" on a coin sized target.
A second type of pinpointer like the Garrett AT and ProPointer not only gives you a continuous beep/vibration at 1 inch or less, they will also give you a proximity beep starting at around 2.5" or so, kinda of like the backup alarm/beep on many newer cars and trucks which beeps faster when you get closer to a large object.
So if you are using a Bullseye II type pinpointer it will tell you there is a target 1.5 to 1" away from the tip of the pinpointer. It won't tell you which side it is on or if it is up or down from the tip.
The proximity pinpointers (which cost more of course!!!!) will tell you when you are getting close and can give you a good idea about what direction the target is from the tip of the pinpointer.
It is similar to your original issues with deciding on a detector. Do you want to get a used proximity pinpointer that is of high quality that will last you a year or two that maybe is even waterproof or do you want to buy a new GP knockoff or a used Bullseye II that will get you started but will not make your detecting experience as good as a proximity pinpointer.
Successfully detecting a target, pinpointing it and recovering it are all determined by IF you can locate it fairly quickly for shallower targets and even deeper targets. Spending 5 minutes or more looking for an elusive target in an already 10" deep hole is not fun when your pinpointer won't let you know how much deeper it is.
Since I use an Equinox a lot in restricted digging areas with screwdrivers only and no shovels, I have my F-Pulse/Tek-Point pinpointers set on maximum sensitivity which is around 3.5". That way if I hit a target and my pinpointer sounds off on it, I know the target is less than 4" from the surface if it is coin sized or is a much larger and maybe deeper target if it doesn't seem to be coin sized. A Bullseye II or the Chinese GP pinpointers will not even make a sound on those 3" to 4" deep targets.
Jeff