If the battery were fully charged every two weeks (because the current draw of the computer will drain the battery in less than a month) there would be no damage done to the battery. However, in the real world, dealers seldom charge batteries as often as they should. As a result, if you buy a car that has sat on the lot for a long time, the battery will probably be compromised, and will not last long after you get it. I would demand that a new battery be installed, before I would buy such a car.
Lifter noise is not nice to hear; it suggests that oil has drained down from critical parts. In a new engine which has not yet been broken in; this can result in more damage than it does in a fully broken in engine. Excessive camshaft wear is one of the likely consequences.
Because the first hundred miles are the most critical, in determining the engine's ultimate level of performance, I would never buy a car that has been used as a demonstrator; and was driven by many people who wanted to test its acceleration, or were just insensitive to the proper way to break in a new engine. For similar reasons, I would avoid a car that has sat on the lot for a long time.
I hope this helps!!!