Can I get full custody or adopt my grandchildren?

My daughter & grandchildren have lived with me since the first grandchild was born in 2005. Except for 8 months of their lives. I have had short-term guardianship of them for about 2 yrs. My daughter just gave them to me & she went to live her life. She don't have a clue who the dad's are. She is a wild girl, she has been with numerous men. She has exposed the kids to all of this. They have seen a lot of things that they shouldn't have. Things that I probably don't even know about. She has been with molesters, druggies, ex-felons, etc. etc. the guys come first, the kids come last. They want to stay with me. I would love to adopt them. What is my better way to go to do what is best for them? What kind of steps would I need to take? Is it expensive to have this done? Once again I am just wanting to provide them a better life & do what is best for them, give them a safe environment.