It’s important be in peak physical condition, but hard to get to that point. You can buy expensive equipment or try and get a gym membership somewhere, but those seem bit daunting after the first or second go. Not to mention that the thought of using something other sweaty people have just used sounds sort of gross.
Having a few things around the house that have multiple purposes is likely a better and cheaper option. Items like the SKLZ Speed Striker are great for cardio, endurance, and will improve your hand-eye coordination. Your reaction, timing, accuracy, and speed will all be put to the test, at either a beginner or advanced setting. It is a squishy ball that is soft and safe to hit, and is attached to a 5lb base that will keep the striker in place, and can be attached almost anywhere. This will cost you $49, but will be a whole lot cheaper than going to the gym.