How is it that deer hunting is so popular?
First you need a suitable gun and ammunition. That's easy enough in here in the US, but it's far from free or cheap, especially if you want a decent scope too.
Then you need to sight it in, especially if you are using a scope. Where are you going to do that? Probably not in your backyard unless you live in a very rural area and have a stretch of flat land that's at least 100 yards long. You'll need hearing protection, a table and chair, a paper target, something to hold the target, and some way of measuring out 100 yards. Then hope you at least "get on the paper" quickly else you'll use up that, say, $50-box-of-20 cartridges before your rifle is sighted in.
If you don't have your own place to shoot and don't have any friends or family that does either, then you'll have to find a rifle range and pay a range fee. The nearest one to me is about a 30-minute drive each way.
Now that your gun is all sighted in, you'll need a hunting license. That's $26 here in Maine, and only allows you to shoot a buck. You can try for a "doe permit," which allows you to shoot any deer, and if you get one (it's a lottery system), that's another $12. You'll also need 2 articles of "hunter orange" clothing here in Maine, such as a hat and jacket or vest.
Now you're ready to go, but where are you going to hunt? If you have hundreds of acres of your own woodland, then great, but you probably don't. So what are you supposed to do? Drive out into the country and go door-to-door asking total strangers if you can hunt on their land?
You've found a place to hunt and you shoot a 300-pound buck. Now you have to gut it and drag it out of the woods. Does that sound like fun? I hope you're rugged and have a pickup truck.
Next stop is a game tagging station, and unless you're a butcher, you'll need to pay someone probably a couple hundred dollars to butcher it for you. And I hope you have a big standalone chest freezer that's empty; you're going to need it.
Despite all this, millions of Americans hunt deer every year.