The great tennis player Arthur Ashe once said, "Start where you are. Use what you have. Do what you can." When it comes to exercise many people over analyze what they should exactly be doing rather than just starting.
Current targets for exercise call for 150 minutes of weekly exercise, breaking down to approximately 30 minutes per day, 5 days per week. Is that a realistic starting point for EVERY person? No. There is nothing wrong with this being a target point for most, but for inactive people it is most important that they just begin by getting active everyday. This could simply mean just a few walks to the mailbox everyday. The 150 minutes per week standard should not hold you back from starting to exercise.
When it comes to exercise it is most important that you find something that you really enjoy doing. When this happens you will leave the "have to" phase and enter into the "want to". I love swimming, biking and running. Going for a 45 minute run at lunch with a friend, or a bike ride with my wife on the weekend is not something I dread doing, but rather a form of enjoyment that I crave every week. Yes, I also like the competition part that comes with racing, but true enjoyment comes from the day to day activities.
Just as I enjoy company during my workouts, you too should enlist the help of a friend or two on this journey. Not only does the "buddy system" help to motivate you to do what you need to do, but also makes it much more fun. Finally, don't compare yourself to other people. We are all at different stages of our life and levels of physical fitness. Remember those words from the great Arthur Ashe, " Start where you are. Use what you have. Do what you can."