Tenting is a cost effective method of killing everything in every square inch of a home. They use a gas that after the tenting, disipates. I believe you will encounter more poisons from residual pestisides that are sprayed all over a house vs a gas that disappears. Termites that have an established colony in a home are hard to kill because they live inside of wood. Evidence of termites in a home usually occurs after a mating swarm. Termites swarm several times a year and even after killing every termite in an area is no guarentee that a new colony wont fly in the week after. The fear of termites sells termite control. Dealing with a problem quickly reduces the amount of damage that will occur. The fact that most pest companies will insure against any wood damage is the first sign that it is a long slow processes. New construction can go to extreme measures to avoid insect infestation but it is hard stop small little things that fly, dig or can walk through a tiny crack in siding or under a foundation. The real problem with houses is they contain wood and it is yummy for many insects. The real problem with termites is that they can damage a structure. They will live where ever they find a "suitable" home. Avoiding insect infestation requires vigilant effort. The key to your fear about this house from my point of view is how much damage has occurred. If you fear, bugs and poison, you will never find a place to live, or work.