Would I be able to be a surrogate mother?

This a weird question for me to ask, but I need to. My older brother and his wife (she has cystic fibrosis) when they get married in 2017, told us they are going to start trying to have a child right away , but it is hard for someone with cystic fibrosis to get pregnant. So I was thinking to myself if it came down to it could I volunteer to carry their child? I am going to be 22 by then but I have never had kids or anything so I don't if I qualify. I haven't even brought this up to any of them because she might get pregnant and have a successful pregnancy. I was just wondering that is all.
Would I be able to be a surrogate mother?
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