Outdoor, free-roaming cats have a five times higher mortality rate than do indoor cats. Cats can be injured or killed by a variety of animals, including raccoons and dogs and coyotes. Most cat deaths are actually caused by getting hit by cars at night, and additional cat deaths are caused by being poisoned by a rat (which has ingested rat-poisoning), becoming infected by feral cats (by FI or FeLV) or even by evil neighbors. Cats also kill wildlife and other pets (rabbits), so it’s a two-way problem.
Many people are fully aware of the possible consequences of allowing their cat to roam free, yet they have made the decision to allow this. For them the benefit of freedom for the cat outweighs the danger and, hey, nothing in life is secure. If you choose this route, you can still minimize the possibility of harm by feeding your cat indoors. Cat food can attract a variety of wildlife, including coyotes, to your yard: try feeding indoors, or if you must feed out-of-doors, do so in the middle of the day when most wildlife is not moving around, and please don’t leave the food out there.
Still, most people want to provide more security for their cats, and the only way to do this is to provide outdoor enclosures and escape routes, of which there are many, many kinds. The cheapest which you could make on your own are long cat poles with platforms on top, or even long (6′ or so) tunnels made of 12″ round piping (you want the tunnel to be wide enough for the cat, but too small for a coyote). Unfortunately, most raccoons can fit into the same spaces which a coyote can fit into. More elaborate options are listed below, which you can either purchase or make.

Long cat walk can be obtained from catbitats.com
Pinterest has some really fun and fine options: https://www.pinterest.com/pin/28640147602279984/?lp=true
Melanie Piazza, Director of Animal Care at WildCare, has compiled a resource list of catio and cat enclosures, and written an article on “Reversing the CATastrophe”. Please visit the page at WildCare, HERE.
Here are two places to obtain 12″ piping: PVC pipe, or corrugated pipe.