Surrogacy Questions

[daisyxs]

hi guys,
i would like to be a surrogate but i cant seem to find answers to a few of my questions.
firstly is the minimum age 18 or 21? or does it differ alltogether?
is there a minimum amount of time that you would have had to know the recipients for?
who actually has to get the ball rolling?
is there a maximum number of times you can surrogate?
and lastly do you have to have finished your family?
if any1 can help it would be much appreciated.
thanks,
Daisy