Rule number one when it comes to purchasing a crossbow is that they are not quiet. Doesn't matter what brand or how new. Some are quieter but they are all loud. But most are so fast it doesn't matter how loud they are. You will be surprised if you have never been around crossbows before and you go shoot some just how loud crossbows are. Even the brand-new ones right off the line are noisy.
Another key factor is weight and length. They can get heavy and long. The lightest you will find is around 8 pounds. That is with everything detached, quiver etc. You also find them to be real long. They can be somewhat cumbersome, especially for someone who has never shot one before. But you will get used to it.
Price is always an object. But I would suggest buying the best you can afford. To fully package out everything that you need to shoot/hunt, you can expect to pay around $800-$1500. For just the bare crossbow expect to pay around $300-$1000. This might seem like a lot to pay for but it will last you a lifetime if you take care of your equipment and follow the maintenance recommendations.
There are two main kinds of crossbows, recurve and compound. Recurve crossbows are more user-friendly for the first timer. Just like everything, less parts equals less breakdowns and it is no different with crossbows. I would suggest recurve if I were a beginner. Some have lifetime warranty on their lines of recurve crossbows. Companies that make compound crossbows offer warranties but most of them are limited. Compound crossbows are not that complicated, they just need more attention and maintenance.
There are also options on how to cock your crossbow. Most if not all come with some type of rope cocking or pulley system to cock the bow. Some come with a hand crank built-in to the crossbow. Others come with detachable hand cranks. Built-in are real nice just because they are handy and you're never looking for your cocker.
There are also options on which type of sights you would like to use. There are open sights, dot sights and scopes. There are many different brands available that are made specifically for crossbows. Make sure to check your state regulations on what magnifications are allowed in your state while hunting. Familiarity, good field of view, durability and light gathering are also factors when considering which type of sight to put on your crossbow.
When you start looking for arrows for your crossbow you will be amazed at how many are available. It all depends on what you want to spend. But I will say this, you get what you pay for. There are some companies out there that will spine test every arrow before they send it to you. Others are just mass-produced. But they all have their place. The most important thing is to get the right weight and arrow length that is recommended by your crossbow manufacture.
When you have picked out your arrow the next thing to look at is which broadhead you are going to use. Fixed or mechanical is your first decision. This is like a Chevy versus Ford deal. Everyone has their favorite. But every crossbow has their favorite also. It is just going to take time and patience to figure out which broadhead shoots best with the arrow you choose for your crossbow. The combinations of these three things are endless. Remember to check your state regulations for which broadheads are legal.