Where do you live? Or did I miss that?

But yes, solid fork mtb, or a hybrid of some sort can be had in decent condition for well under $150. If it were me, and a first time commuter, I'd spend ~$75 on something rideable, then spend the rest on excellent, durable, and relatively fast commuting tires like Schwalb Marathon Supremes.

I'd take an ugly, semi-rusty bike (as long as it rides smoothly) with excellent tires than a mediocre bike in excellent condition with garbage tires.