Getting them to show...I dunno, but I've used things like phone cards or gift cards to get people to show up to fill out paperwork, etc. People like free stuff.

If you pay them, and they accept the money, does consent still factor in?

Ethically, maybe, but when there's been no irreversible harm, other than not being able to get pregnant for X weeks, I think (IMHO) it would be harder to take it into court.

Now, if there was some allergic reaction or something to the shot that really messed her up, I can see it being called into question whether she was able to give informed consent.

I think if it were me, I'd design the consent form to ask if they were under the influence of drugs or alcohol at the time of signing, if the target group were addicts. Like they do at plea bargain hearings.

cm