Riding lawnmowers are excellent for cutting grass in big yards. You don't have to push anything, you don't have to walk and you can cover a large area in a short amount of time. However, if all you have is a narrow strip of grass in front of your house, then maybe you should reconsider buying a riding lawnmower. Also, if you have a lot of trees or other obstacles in your yard, it may be more practical to buy a push mower to get around these things.
Have you thought about where you would put your riding lawnmower when you're not using it? You should have some kind of shed or covered space for it. Ideally, you'd want to store it in your garage to protect it from the elements and keep it nice. Your riding lawnmower is a vehicle just like your car is, and you'll need to store it appropriately.
Riding lawnmowers are expensive. And because it's a vehicle, maintaining it is more expensive than maintaining a traditional push mower. It will take more gas and more oil. You need to buy and replace filters for it, and replacing the blades when they get dull is going to be more expensive than it would be for a smaller mower. So even after the initial cost of buying the riding mower, you're going to be spending a significant amount of money on it the whole time you own it.
You've invested all this money into your riding lawnmower, so you better be getting some good use out of it. It simply isn't practical to invest in a riding mower if you only need to mow your lawn once or twice a season (such as if you live in the Southwest, where it's so hot the grass grows very little), or if you plan to move to a smaller place within the next few years.