purchase a few $100's

maintanance almost zero.

but in order to be comfortable with the gun, you should go shoot it in a shooting range periodically; you need to buy ammunition for practicing.  These can cost you up to a few hundred dollars a year, depending how much you train.

you can also buy a nice gun for a few $1000's or more.  there is no limit if you want to go high class ...

also, once you buy a gun and get to know the firearms, most likely you will want to buy more guns, different types ...