I want to adopt my grandkids. Their parents (my son and daughter in law) are unfit and druggies. They have parties with the kids around all of that. What do I do and how do I start preparing? How much would this cost in legal fees?

It sounds like you are seeking an actual termination of their rights (as opposed to a simple guardianship of the children). Termination of parental rights is a very difficult case to prove and is very fact specific. The Court is hesitant to take away rights and will only do so under specific cases. In this case, it seems like you might be able to try and show that the parents are not fit to care for the children due to their being addicted and/or under the influence of drugs, etc. Remember that you must actually prove that they are using and/or under the influence of drugs and that they are not acting in the best interest of the children. Having parties and drug use in and of itself may not be evidence enough to show that these parents are unfit. It takes proof to show that they are acting in such a way that the children should be removed and their rights terminated. The best step to take in your case is to consult with an attorney and begin preparing the matter with him/her to reach your goal.