My sinks are all plywood. The only sink I ever bought was a 5' pvc sink that I used in my apartment in CT. I could only work at night. My kitchen was my darkroom. The work table and enlarger was set up on one wall. The sink was placed on top of the stove with the garden hose drain into the sink. Working with 11x14 trays was challanging to say the least.
All my other sinks are home made from 1/2" exterior plywood, finished on both sides. I used resin to seal them up, the kind used for surfboards. You can buy pigments if you want colors.
One thought, the light over your sink that you use to judge the exposure of your prints should be of low intensity. If it is too high, you will over print. I use a 60 watt bounced off the cieling. Wet prints ideally should be dried before making determination. Keep a blow drier handy.