Are vocal cord nodules bilateral? Can they become cancerous?

It depends,, It depends on the cause of the nodules/lesions. Lesions from overuse or misuse of the vocal cords like loud yelling are usually symmetric and bilateral, and rarely progress to anything harmful. Those from cancer are more likely to be unilateral and irregular. Either way it's wise to see your doctor if you have any symptoms like hoarse voice to be sure what the cause is.
Nodules and cancer. Nodules by definition are benign (not cancerous). You can think of them like callouses on both vocal cords, typically from voice abuse. They do not turn into cancer. The main risk for cancer of the vocal cords is tobacco use. Talk to your ENT doctor about what you can do to treat your nodules. If you smoke, now would be a great time to quit!