I participated in House Hunters about 10 years ago. The buyers were real. Two of the three houses they looked at were really for sale and had really been on their list. The third was one we went out and found for the sake of visual interest. In fact the buyers looked at only two houses, and bought one of them. The show needed three contenders to fit the script.
When it comes to HHI, for sure the producers don't want to travel to a far-flung location and film a house-hunt with an unknown outcome because if the people don't buy there is no show.
HHI contacted me asking if I had a client who fit a certain profile - buying property (really), intending to move to Belize, and being attractive/articulate enough to be interesting on TV. So to the degree that the storyline was pre-qualified, it is "staged" but the story was more real than not. I had not seen the show (20 years of voluntary no-tv lifestyle) and initially I wasn't at all keen on participating, but the idea that Belize might get some exposure seemed ok - they sent me a couple tapes of the show and I liked it so I said yes. FYI - this show doesn't result in the phone ringing off the hook with buyers. I did however hear from lots of long-lost friends and relatives, most asking if I go barefoot all the time.
The buyers were paid a minimal amount - I think $1,500 US - for their time. They paid all of their expenses for participating.
The film "crew" consisted of three people - a director, a fellow carrying lights and a camera-man. Camera and lights were portable. They absolutely did not disrupt the homes during filming. Having worked a long time in LA, and around the film industry (houses we had for sale being in films etc) I was very skeptical of working with a film crew, anticipating damage, mess and chaos. HHI did not damage a thing, barely moved a stick of furniture. The crew was just about the nicest happiest bunch I have ever met. Perhaps it was just the luck of the draw, but they were FUN and complimentary and just plain nice/respectful/helpful.
I was asked to do a second show but the clients I contacted were reluctant to appear on TV - they were real, but had issues (jealous ex-wife, cautious accountant ...) In the end this show is about fun and 15 minutes of fame.
A brilliant business idea from HGTV - long shelf-life for the shows, minimal cost for production.
I believe the the rules of engagement for HHI have changed to include a lot more fabrication of story than before - but as they say in the world of theatre - 'Suspend your disbelief" and enjoy.
AmbergrisCaye.com 
