Agreements, apps & adoption

Hi! I have pot bellied piglets that I am fixing to put up for adoption. I am wondering; is it very important to have some sort of a contract or written agreement between myself and the person adopting? What should it contain? Also, I am very concerned about what kind of homes they may potentially go into. I have already stressed to interested parties the importance of doing a lot of research before you make the decison to adopt.
   
So far I've received quite a few e-mails in response to the ad I placed. The e-mails are asking me the basic & standard info like their color that I clearly stated in the ad. They also send 2-3 e-mails, one right after the other, asking these things. I have wasted tons of my time that could have been prevented if they took a couple of minutes to review the ad. I don't mind answering questions at all; in fact, I welcome and encourage it. It just makes me wonder if they are going to be able to do proper research and provide a good home if they can't pay attention to the very short ad. There could also be other reasons for that too, other than not paying attention. What do you think? Should I ask that people wanting to adopt fill out an application covering a few basic questions pertaining to what the piglet's living arrangements would be, or am I overreacting? Any tid bit of advice or experience that you may have will be greatly appreciated. Thanks.