a used exercise bike is a great start. That and walking here and there, and you're all set! Good for you for jumping in and doing something positive for yourself.

A hint on moving that bike. Most of them have one free-spinning wheel. Turn the tension all the way down, lean the bike so all the weight rests on the wheel, and you should be able to wheel it across floors. Up stairs, tho, you will still have to lift! (Can you tell I've moved mine a few times?)

Remember, five minutes on it is better than nothing. Don't start using it to toss clothes or newspapers on--keep it clear of junk and looking inviting!