The hardest thing is having the will power to keep it up. but a few months ago I brought myself a sit up bench, because like many peeps, I was quite slim but not toned. At first I found it really hard to motivate myself because it was quite hard work and after the first few sessions my body ached all over like my stomach area had been a punching bag. Although it hurt a lot, everyone said to keep going, and I did 3 months later I have gone from doing 20 sit ups every other night to doing 250 5 nights a week with other stomach crunches like Pilate's and also a 2 mile run most nights. My abs are looking great and I feel great too, and all without going to the gym.
My advise would be to get a good pro sit up bench, with your stepper and rowing machine you should get that toned tummy quick. You can also get a bicycle and ride it hard and fast until you are exhausted and then ride it back home and take a shower. You will be amazed in a very short time at the improvements in your physique. You might also get one of those 'baby back carriers' and carry a kid in it while you bicycle. The kid will enjoy it and you will have the same or even better results.
