Wow, another thread about adoption.
First let me say that if you are ready for a roller coaster of emotions GO FOR IT. First and foremost though, it is harder to adopt domestically from an agency when you already have two bio children UNLESS you are wanting to adopt a special needs infant or an infant of another race. Adoption can be costly, luckily there are tax credits up to 10000 and even higher for a special needs adoption.
Our son was adopted at birth, we are in an open adoption with his birthmother, and we met her on the internet. She lives 2000 miles from us so there is no visitation at this time. Our son is biracial and he has fetal alcohol spectrum disorder. My husband and I were only interested in a transracial adoptoin and we were open to various special needs. I think you need to know that when adopting a child with special needs you really need to be aware of how to handle those special needs. With these children you will be seeking a lot of help from the mainstream world, and sometimes the attachment parenting we are used to using with our other children doesnt always work well with children that have drug or alcohol effects. (i learned the hard way)
There are so many babies in the US that need loving homes. African American baby boys are the least desired in adoption, then biracial baby boys. Other children that are hard to place are those with Downs, Cleft lip/palate, or have a family history of mental illness.
You can adopt fairly inexpensively or for free through the state, though you will have to jump through hoops to do so. Fost to adopt situations can be an emotional roller coaster but you can just adopt through the state.
From personal experience, when considering adopting a child with special needs you really have to take into consideration the other children in your family. I had to devote a lot of time and energy more than I ever believed I would to my son after he came home and it really took away from my daughter. We as a family were not prepared to deal with all of these things and my daughter got the worst end of the stick. Now things are fine, I even had a baby when our son was 17 months old, but it has been a hard adjustment for her.