It depends what you want to do with your website.
There are grossly two models:
Right managed: You set-up price, size and conditions of use of the picture by buyers. You can limit it by country, region, number of use, support etc.. Look at Getyy or Alamay to see how they licence their right managed images.
Royalty free: The buyer can do almost anything he wants. The model itself calls for low wages and copyright abuse.
If a buyer doesn't respect the license model he agreed with you (like using a image twice while it was contracted for one use), you have to pursue him, otherwise you will lose a lot of money. Some buyers do it by negligence, other know perfectly that they are cheating.
Most of time the wrongdoer will comply if he knows copyright laws are on your side. An email is enough in 90% of the cases. However, if you sell your pictures as a business on your own, you have to be prepared to use a lawyer for those who abuse and violate your copyrights. Here too, with time, you can make money.
The positive thing is: You are not protected more on Getty, Alamy, i-stock or others than on your own website. You have to defend your right and wages in any case.