Joe P I feel Jim Johnson is exactly correct but believe that to be the case for houses. It's a perfect system for those buyers/rentors slightly more "do it yourself" to politely put it.
One of my mentors uses a system similar to Jim's and goes a step further with an automated message system. The message has to be listened to and then the person can get access to the house on their own.
I think this is a great system and I KNOW both work for houses, however I found that they don't necessarily work with mobile homes. And there are plenty of things I could say about why, however due to the topic presented I will say that I've given all the information I KNOW on a home in any given ad/website post/etc. and STILL get a TON of phone calls on each property.
The more I elaborate on my ad and give all the information needed the "dumber" my phone calls get. That's when you get the calls from folks that have nothing else to ask than "Is it still available", and I agree with the response already posted about just chatting.
However, I've got a theory on why this happens and what to do about it. I think the typical person calling regarding a mobile home is used to being in a rental. I don't think many have had the opportunity placed in front of them to take ownership in a place. The systems set up by landlords are usually much different than set up by brokers/owners/investors/etc, especially pertaining to mobile homes. I've run into a lot of individuals owning and renting many mobile homes and their "system" has all been the same. Advertise for phone calls and put the first qualified renter in place. Therefore, it's safe to say that the mobile home renter turned buyer for your purposes has been fairly conditioned to call a number for each time they want to rent. To kill the point, can you remember a sign in a mobile home with JUST and email address or website address that was with a landlord NOT an investor? ALL landlord's I've ever come across just put a number in the window thus conditioning the phone call.
To "fix" my phone call problem I hired. But it doesn't have to be paying someone to sit around answering phone calls. In the beginning, I fielded the phone calls, immediately "extracted" their buying criteria and urgency, and immediately sent them to my contractor. So what I did is had my contractor that works on homes for me answer phone calls and subsequently show properties.
It's not rocket science, but I think knowing the WHY behind the "problems" can get you a long way into knowing what solution to take. Basically for all my trial and error (and sitting in your shoes as a one man show fielding about 10 to 60 phone calls a day) I found that I'll NEVER eliminate the calls, only figure out better ways to handle them. I'll end by saying there's a LOT more to this and I haven't addresses all of your "concerns", however handling the call volume is a BIG piece of the "buyer puzzle".