When I turn the wheel even when the truck is off and parked the driverside squeals what could it be?

 

Had same on my 99. Was bad ball joint. Had to replace whole upper A-arm as ball joints are not replaceable. I went the long way and replaced both upper
and lower control arms as well as tie rod ends. My PU has 220,000 miles and was never done before. I probably did more than was needed but
I am good for many more miles.

 

Outside the excessive squeaking what will happen if I don't replace them? I plan to replace them but have to wait til payday

 

You should be alright for a while. I drove mine with the squeak for about 2 months. Eventually, you will get excess wear in the ball joint causing
alignment problems. Worse case scenario is the ball joint completely fails and the front end separates, but you have I believe you have time before that happens. I
heard people say they drove for years without problems, but I wouldn't be comfortable doing that.
If it concerns you, YouTube how to check for bad ball joints to access your situation.