Fitness doesn't have to be expensive. Most people think of home gyms as elaborate affairs made of heavy metal frames or sleek high impact plastic ones, with weights, pulleys, and other gadgets sticking out of them.
While these home gym systems are effective, you don't necessarily need them to stay in shape. You can actually build your own gym equipment, using simple exercise gear that will allow you to work out without placing a large dent in your wallet.
The first and simplest piece of equipment you can use is a clean soft floor mat. Make sure it's wide enough to accommodate your body lying on the floor full length, and thick enough to cushion your body from the hard wood or concrete of the floor. Don't make it too thick or soft, as this will throw your balance off when it "yields" under your body weight.
Rubber mats work best for this purpose. This mat can be used for sit-ups and crunches, as well as simple calisthenics like jumping jacks and running in place. Free standing squats on the mat held build up leg strength considerably, too. Even before you start building your own gym equipment, using a simple mat that you can pick up at any department store can already go a long way.
Another exercise tool you can make when building your own gym equipment is push up bars. These are simple and easy. Find a pair of U shaped metal bars, with the bottom of the U fitting your hand's grips comfortably. The ends of the U are then fastened to either wooden blocks or metal sheets (your choice) that will let you place them on the floor. You can wrap the "grip" portion of the bars in foam or heavy tape to make your grip better.
Studies have shown that push ups done when the hands are in a straight fist position are better for the wrists than placing your palms on the floor. These simple handle-bars allow you to do push ups correctly, and from any of the various positions that push ups are done from to hit various pectoral muscle groups.
Another piece of gym equipment that's easy to build is a chin up bar. I highly discourage the classic approach some people take of mounting these on a door frame, as this can lead to accidents when people walk in on you. Instead, get a long comfortable bar and mount it one and a half to two feet from a wall. Use mounting and support brackets to ensure that it can take your weight. Set the bar's height at just high enough for you to reach on tiptoes. This height is ideal because you can get enough ground clearance by simply flexing your legs slightly when you do chin ups.
The reason the bar should be set so far from the wall is so you can do pull ups both facing towards and away from the wall. Also, if you want to, make the bar long enough so that you can use a "wide" grip, with your hands positioned past your shoulder's width. This allows you to target your lats when you work out.
Another variation of the above gym equipment you can build is a device used for tricep extensions and rowing exercises. This is a simple metal bar set horizintally at a certain height. To determine the height of the bar when building this piece of gym equipment, lie down on the floor and extend your arms straight up. This is the height the bar should be at. Set support bracket legs at the ends of the bar so it retains it's height. Make two sets of these bars, one for your arms to grip, the other is a place where you put your feet on.
Two exercises can be done with this set. One, you can lie on the floor underneath it and "row", pulling yourself up in a reverse push-up. For the other, you place your feet on the other set of bars, and position the "arm" bar right behind you. The position looks akin to sitting on the edge of a chair with your feet up on a table, and your hands directly behind you gripping the bar. You basically raise and lower your body using your arms. This works out your triceps and gives them a great deal of definition.
The above ideas are just a few examples of how with a little imagination and work, you can build your own gym equipment easily. It helps if you actually have prior experience in a real gym working with free weights and other exercise machines, as you will know which exercises target certain muscle groups.
However, if you want to build your own gym equipment and have no prior experience in working out, I highly recommend going to a real gym and getting some exposure first before you get too creative, as any mistakes when building your own gym equipment may actually lead to personal injury.