As a former lawyer, I see it like this, people pay for all sorts, they pay for sex, why not a womb? As long as proper checks are done and a contract agreable to both parties, represented by competent counsel is arrived at, what's the issue? I've toyed with surrogacy myself, after having 3 of my own. I needed cash, I carry babies real good. I never did do it, but some people want babies and can't have them, other people can carry and birth a baby.
Should they be paid? Uh, yeah. Months of interruption from their regularly scheduled life, the physical toll pregnancy takes, fuck yes, they should be paid!