@BirdsBikeBinocs Correction, this type of bikes is called BSO - Bicycle Shaped Object. It is because they are not real bikes though have a similar shape.
@Freestylexgp For $100 your only chance is to find something used. And you'll need to search hard to find something decent at this price point. And prepare to invest more to put it in decent shape. Cheapest new bikes usually start at about $300-$400. And they are sold at bike shops. And they will be very entry level bikes. But not BSO.