Raise or convert your cat as an indoor-only cat.
This is of course, the least expensive way to protect your cat from outside dangers. There is a common perception that cats must live outside in order to be happy. Cats can be perfectly happy in an all-indoor environment but there are some caveats. A single indoor cat will be much easier to manage than multiple indoor cats. Indoor cats may require more interaction, playtime and attention from their owners, in addition to the use and inconvenience of litter boxes.
- You will need at least one "scratching station" for each cat to keep your furniture in good condition. Basic scratch boxes, posts and similar commercial products are fairly inexpensive.
- Cat toys and such, but you don't actually need to buy anything. There are plenty of items around the house which can be made into cat toys. Our cats are perfectly fine with a wadded up ball of tin foil, or piece of cardboard hanging from a string.
- Cat grass as a dietary supplement.
- Dried catnip (optional)
This one I built is connected to a larger cat-safe yard but the concept is the same:
This one is a bit more elaborate, but the materials cost was under $50:
I have also reviewed several commercial products that allow your cat to roam outside in the safety of your own yard. The review is a bit old but these products are available and there are quite a few options if you do some web searching.