Hello B.,
I was a surrogate mom 9 years ago. I was a "gestational surrogate" meaning the baby's were 100% biologically their parent's and had no biological ties to me. I was just "the oven" so to speak.
I ended up having twins. I wouldn't take any of it back for a second, however, it's a very involved process and takes a lot of dedication.
Additionally, I personally think it's best done once you have finished your family and are quite certain that you don't want anymore children of your own.
You are on a strict medication regimine, which requires you to take medication, and give yourself injections (or have someone else do them) at very precise days/times. Once the transfer of the embryos takes place, you must till continue on the medication for about three more months until your body figures out that it's pregnant and takes over in the production of the hormones that will sustain the pregancy.
People always ask me if it was hard to give the baby's up, but emotionally, my mindset from the get-go what that they were not my babies and I was simply helping another couple. Don't get me wrong, though, you definitely develop a bond. I am very lucky that I am now considered "aunt J." and I keep in touch with the family. They live on the East Coast, so I don't get to see them as often as I would like, but I am a part of their family and they are a part of mine. I would assume not all surrogate cases happen in this manner and some people might not ever speak to the family again...not sure.
Being pregnant with twins was very hard for me after the easy, complication-free birth of my own children. I ended up having a cesarean, and the experience honestly ended my desires of wanting to be pregnant again (which was okay since I had already had my own children!). But, again, I wouldn't take it back for the world.
Oh yea, additionally, there's a LOT of legal paperwork involved as well.
I would be happy to answer any questions.
Good luck on your decision!