To start you buy/sign up for a contract with Dish or Direct TV. They will provide the box receiver and the antenna receiver. There may be an initial sign up special price but after the contract period (12 mo typically). The price goes up. If you want all the premium channels you will pay around $125/mo if you only want the basics around half that. Plus your equipment rental fees.
You can find the antenna and box on Craigs list for very little $$ if not free and avoid the equipment rental free. I just took a remote, box and antenna down to Goodwill last month.
If you can read a compass and understand where the equator is in relation to your location on earth, then you can set the antenna yourself. IF you do not want to learn that skill you can pay for a antenna that figures it out for you.
IN short it can be a $50 or $500 cost to set up on top of the monthly subscription fee.
AS for how good they work. I always had excellent reception and was able to set my antenna up in 5 min. IF I had a clear line of sight to the southern sky. If you park where you cannot shoot the satellite then it does not work.