Shut the front door!

[Seth Williams]

Hey All, I own 2 duplexes (4 units total), and I'm looking to replace the front doors on each unit (the current doors are pretty beat up and they don't insulate well). Does anyone have any good recommendations on what kinds of doors I should get? How much should I plan to spend on each door? Should I go for metal or fiberglass? Windows or windowless? I'm just looking for some candid thoughts and opinions from the seasoned pros. What do you think?