I value my own free will too much to become voluntary. It's that simple. I don't care if I was homeless; even you are oppressed by your environment, you can always retreat to your own mind with your own free thoughts, without someone staring in at them, or forcing you to go against your beliefs. I would never give that up. It doesn't matter how bad your life is now compared to how great it could be as a controller; if you aren't living that 'better' life yourself, the point becomes moot.
What I might do, if it were possible, would allow them to be an observer; to somehow inhibit their ability for complete control. They could watch watch I do, experience the senses, but they would not have any power over my body. I could temporarily allow them physical control, but I could instantly return control to myself at any point. Also, I would want the ability to shut them out completely; put them in darkness, so to speak, if I was doing something I would want privacy for. After all, if they had full control as a Yeerk like in the books, the converse is exactly true, aside from the ability to shut them out. Still, even with all those limitations on the Yeerk's power, I would still be incredibly reluctant to allow it into my head.