You need to look up surrogacy laws (or lack thereof sometimes) in your state. My boss is being a surrogate right now, she's about 7 weeks at the moment. She's done it once before about 5 yrs ago. The first time was for her aunt and she had twins. They were laying the wrong way or something so she had to have a c-section (and she's very educated on pregnancy/birth so she didn't get bullied by the doc I'm sure). This time around she's carrying twins again and they are forcing her to have a c-section. Their reasoning is that there are no actual studies showing that having twins vbac'd is safer than a c-section.
With her first surrogacy she lived in California and she said the laws there were really good towards it. However they didn't go through a lawyer and she ended up not getting paid everything she was supposed to, not having her maternity clothes purchased for her, and other things like that. This time she's doing it for a mutual friend. So they went through a lawyer. They agreed to only place 2 embryos inside her because she doesn't believe in selective abortion had all the embros survived. It's completely written up that she gets certain things paid for (including a maid in her 3rd trimester!!). Another thing was that she had to agree to follow the advice of her OB or midwife (which is why she'll have to have a c-section again). Also if anything turns out to be wrong with both/either of the babies than the biological parents must still take care of them, etc. They can't just bail out.
It's a complicated process and it can be painful. She had to do hormone injections before having the embryos placed and she was bruised all over. At 7 weeks she still has some hormone creams and such that she has to use. It's definitely something you want to think long and hard about. I think I would have a hard time giving birth and then just coming home with empty arms, kwim?