I am considering getting a pullup bar. They have them for about $40 at Big 5 and they appear to just slip in and wedge themselves into the door frame somehow to stay up. I'm not sure of two things:

1) Will it cause damage to the wall above the door, the moulding, or the rest of the wall/door frame?

2) Does the door frame require moulding around it to work?

Alternatively, is there something else I could use for pullups, especially something that is low so I can get a good start. I can't even do one pullup. I suppose maybe I could walk a mile to the elementary school but maybe there's something I'm not considering that will work closer to home?