You can do that if you choose, but it is not as effective as drilling the slab inside the garage. This is because the garage is a separately poured slab, meaning the termites could come from deep underground and come up to the surface under the garage slab, and enter the wall where your door is going into the house untouched. You don't have to drill every wall in the garage, just the walls that are not exterior walls, where you have living space on the other side of the garage wall and apply Termidor. So it is a personal choice, but drilling the garage walls is the best way to protect all entry points.
We cannot answer that question for you. You are definitely not required, however, if your state requires a termite letter at the time of closing, only professional companies can issue these letters and if you do not have an active contract with a company you will usually be forced to pay a large sum to have your house treated to get a clearance letter. You should call your state Department of Agriculture which is usually the department that manages pest control companies and ask if your state is one that requires a termite closing letter when selling a house.
You should perform a liquid termite treatment in the ground to get the termites where they are entering your house. To perform a treatment just as a professional company would do, please read our How To Do A Termite Treatment Article which explains exactly how you should treat your home properly. Doing a treatment like what is described in the article will not only take care of existing termites that you have, but it will also protect and prevent future termites from entering for about 7 years.
Here is a a link to the article: http://www.domyownpestcontrol.com/termite-treatment-c-3_352.htmlYou should perform a liquid termite treatment in the ground to get the termites where they are entering your house. To perform a treatment just as a professional company would do, please read our How To Do A Termite Treatment Article which explains exactly how you should treat your home properly. Doing a treatment like what is described in the article will not only take care of existing termites that you have, but it will also protect and prevent future termites from entering for about 7 years.
Here is a link to the article: http://www.domyownpestcontrol.com/termite-treatment-c-3_352.html
Please let me know if you have any further questions.