Welcome Adan! I am a 2-wheel convert myself. The Miata is the almost as much fun as a bike...plus it has heat, AC and a top when you need them.
If you're looking to spend $4-5K, you're better off buying from an individual rather than CarMax (or similiar). If you do find one, you could probably convince some members here help you give it the once over. Wouldn't be the first time we did!