I just gave birth as a gestational surrogate in January. It was an amazing experience and I'm strongly considering doing it again. There are many requirements to consider. A few that most fertility clinics require:
Support from significant other
Carried and care for at least one child
Background check and psychological screening
No STDs or other infectious disease
No welfare or other financial assistance
Usually between the age of 21-40
BMI under 30ish (this can vary)
Just some info. Definitely good to do lots of research before jumping into anything to make sure it's right for you and so you can be aware of potetial problems. My experience was awesome, if you have any other questions feel free to ask.
Good luck with your decision!