An adoption is a two-step process. You need to have a relinquishment with the biological parents followed up by an adoption by the two of you. So, there are actually two separate cases. The relinquishing parents need to go through counseling with social services and the adoptive parents need to do the same. So, the big expenses are the counseling costs, the court filing fees, etc. The attorney fees will probably be in the realm of $1,000-$1,500. Best wishes
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I would suggest that you first visit the official Colorado Judicial Branch home page: www.courts.state.co.us/. If you click on the tab "Forms" you will find a tab for adoptions. Within this section you will find requirements, forms and instructions for a family or kinship adoption. These instructions will provide you with information as to what steps and forms you need to complete for the adoption. All the forms referenced in the instructions are also contained in that section. It may be that you can complete the adoption on your own. Since your grandson is over 12 years old, he will also need to consent to the adoption.
The filing costs for an adoption are $130.00, there are also costs for fingerprinting (varies), Trails background check, $33.00, and other misc. expenses, like service and/or publication costs. If you can't afford these costs you can request a waiver from the court.
Even if you retain an attorney, having this information will help you better understand the process and will help you assist your attorney.
Mr. Leroi's description of the mechanics of the adoption are correct, however to clarify, the relinquishment and adoption proceedings generally run concurrently. In addition, in your situation, you may qualify to have the home study/counseling waived. You will find a discussion of the waiver and the required form in the family/kinship adoption section.
The question that pops out to me is: where is the father and does he consent to the adoption? If this is an issue, I would recommend that you consult with an attorney.
You can hire an attorney to just give advice, assist in filing out forms or to completely represent you. The cost of hiring an attorney depends on the complexity of your case, particularly if the father contests the adoption.