These are some great points and I left it out of my original message, but that is always something I have worried about, not knowing the value of advice that I do get.

Nevertheless, I have a real need for someone who can at least take the functionality concepts that I describe and tell me if they are technically possible, describe the level of difficulty, explain any problems etc...

I have built a number of websites using freelancers and in almost every case, I left some technical description off of my rfp because I did not understand the way the underlying technology had to be structured in order to get the desired functionality.