I have 2 pull-up bars available, these are designed to screw into ceiling joists which provides a strong, secure mounting. One is a simple bar used for pull-ups and chin ups, the other has hand grips with long suspension lines. This latter setup was intended for us more senior health conscious folks, where you can lay on your back and pull up with your heels on the floor. As you gain strength you can put a stool under your heels, then a chair, thereby increasing resistance in an easy and adjustable manner. When you're buff you can shorten the suspension lines and pull yourself up to the ceiling.
The hand grip set up should cost more but I just need the space, so my loss is your gain (the price is per each). By the way, many pull-up setups these days are supposed to hook over the trim above a doorway, but having installed much of that trim I know that in many cases it's lightly tacked to the wall and there's a risk of pulling the trim off and bouncing yourself off the floor.