About 20 years ago a small group from an organization I was involved in met with an architect to start talks about a new, large building. The architect took an approach to which I had never been exposed. He said he didn't want to talk about square footage, rooms, walls, or anything like that. He started out with a big flip chart (blank) and wanted to talk about activities, number of people, what was needed to support activities, timing, and how people moved from one space to another. After all this was bubbled out, it was easy to slip into matching spaces and such to the activities and traffic. As mentioned, you need to talk about and figure out what "snow-birding" means to you. Will you move every few days or will you make one long trip to your summer destination and stay put until you return? For some people, a motorhome towing a car is the best solution. For others, a travel trailer or fifth wheel with a tow vehicle is the answer. They each have their advantages and disadvantages. Start out by searching and reading the forums - even check out the Escapees forums and RV-Dreams.com.
Rob