Not all generators will come with the automatic transfer switch included so you may have to order that as an accessory item and a 12 volt battery needed for start up that can be purchased at a local auto supply store. Some other options can include a remote operable digital display for inside your home.
There are so many things to consider when purchasing a generator. Mainly you have to decide, do you want to control your whole house or just emergency loads? This will have the biggest effect on the size of the generator and the controllers.
FYI - The permit process for this type of system if you are acting as the general contractor:
Before you purchase a generator, bring a copy of your property survey to the local building dept along with a sketch of where you want to install the generator. This will normally be as close to your electrical panel and gas piping as possible. They will then let you know if you can install it there based on the property set backs from your neighbor's property lines. Just like a central air conditioning unit, there are set back requirements for noise and in this case emissions too so you can't be too close to your own windows.
If you are approved, pick up the permit folder and have your electrician and plumber fill it out and you will fill out your portion as the general contractor and submit the permits for approval. Once they are approved, you can go ahead and order your generator and create a "pad" like the one shown made of crushed stone, concrete, or a premade composite pad like the one shown over crushed stone. Then give your contractors a call and we'll do the rest!
*Keep in mind these units can easily get over 400 lbs.
Here's a great tool for sizing your generator, they don't have to be that big to get the job done. Just pick what you want to control and the tool will calculate the size and recommend an generator and transfer switch.