It may seem an obvious thing to say, but when you decide to foster, something very big to ask yourself is whether you have the where-with-all to commit. Taking in a child is no small thing, and I guarantee, the road WILL get rocky sooner or later. It's not always a bed of roses to care for a child that is not yours biologically.
Adding to that fact alone is the various issues that will arise due to trauma and/or neglect that the child has gone through. They have experienced loss, and it reveals itself in so many different ways.
Hopefully, as you all adjust, you become a safe place for your foster child. As such, you can expect some very honest behavior. The question is, do you have the stamina for it? Will you be able to see the case through to the end, whether that end is reunification or adoption?
I guess what I'm saying is that this is not a decision to take lightly. The days can be long and difficult, and sometimes with few bright spots. One needs to consider the long term effects to their own bio family, the foster child, and if they can truly commit.
This may seem like a negative post, and I don't intend it to come across that way. But I do feel that families need to count the cost carefully, and know their strengths and weaknesses. You won't be doing any potential child, or yourself, or your family, any good to take in, and then possibly re-place that child if you decide it isn't working. On the other hand, the feeling that comes when you know that you know that you will see a child through their conflict is a great one, and you can do something amazing in that child's life when they know you are that stable place for them.
Pray, talk, count the cost, then do it.