It would be a lot of work to try to keep something like that up to date with the Form Builder I think too. Mostly the issue would be having to constantly update it every time a property is off the market and every time you add new ones. You would have to constantly change the drop down menus or whatever you have setup for it each time that happens. You'll have to do this regardless of what software you use though, so to be honest I guess it could be done fairly painlessly by using dropdown menus with the house ID or whatever you use to identify the property. Just put that into a dropdown that they can choose from.
When you setup the email results, set up that field then to be the Subject of the email response. You will always know what property they are interested in that way. I'm sure there are other ways to do this, but to me that would probably be the simplest one.
As I said, it will still require work in changing it out for any property changes, but you would have to do that for databases too or any other means you try to do this with.
P.S. A more simplistic way would be to make a box for them to fill in the ID or whatever you use to identify the property. This would require the property hunters to fill it in of course, but it's a way to do a generic form that works for all properties.
Just be sure to put an example of the ID you want into the box (use the setting for this, can't recall what it's called in the program lol, just makes it a light grey placeholder or something like that) so they will always know exactly what you're looking for in that box.