What are the top features to consider when purchasing a folding bike, specifically a Schwinn model?

When purchasing a folding bike, especially a Schwinn model, consider the following top features:

1. Frame material for durability and weight
2. Folding mechanism for ease of folding and unfolding
3. Size and weight when folded for portability
4. Gear range for different terrains
5. Comfort features such as seat and handlebar adjustability.