How to become a surrogate mother?

i am 21 and 290 pounds i have a 5month old son who is beautiful...i need to help support my son and to get my own home..i was thinking about surrogacy...but all i see is that you have to be a certain weight yes i know they want you to be healthy where nothing goes wrong...but i had my son with no problems..it was a great pregnancy with no problems i did however have to have a c section because he was just to big...but other than that we were both healthy...i guess my question is how do you get around the weight issue and. where do i look? should i advertise myself?