More is not more. Much fatigue is actually caused by muscle tension from the stress you have had that day. A flight of stairs is about 12 steps. Twenty flights are equal to about a mile, or 100 calories. No need to buy a stair-climbing machine.
Stairs are just about everywhere.
A 30-minute workout may sound formidable. You can get just as much benefit by breaking it up into three ten-minute sessions. Time traveling to and from, dressing and undressing, and showering can all add up to about 30-40 wasted minutes. You continue to sweat for 30 minutes after you stop exerting, so you are still sweating when you dress to go home. Also, memberships cost about 50-100 bucks a month.