There are a number of issues you should address in your business plan regarding the choice of a facility. Not surprisingly, the most important consideration is usually one of location. The first question to address is why you need a business facility. At one extreme, a consultant may perform most services in space provided by clients. That consultant may not need a facility at all and may maintain a small home office to store reference materials and business records. At the other extreme, a manufacturing business may require, for example, access to rail transport, room for manufacturing operations and storage, parking facilities for a lot of employees, etc.
Once you have assessed your facility requirements, you'll also want to look at the cost. There are numerous factors, some unrelated to your business, that will figure into your planning. For example, you may be faced with the choice of leasing property or buying it outright. The trends in the local real estate market could have a big impact on your decision. If real estate prices are rising quickly, buying may provide some protection from the risk of escalating rent and afford a way to mitigate losses if the business doesn't work out.
Your business plan should also describe the basic aspects of your facility (age, size, general location) as well as the important aspects of any equipment that you may need for operation.