The computer hardware simply executes the software instructions, and just about any new machine sold today will run business software just fine. Computers are tools, and every few years, you're going to need a new tool. A Notebook Sales is a mobile business. There is really no reason for a salesperson to buy anything other than a notebook computer. In the past, these small units could not economically rival the power and features of desktop units, this is no longer true.
Most people place too much emphasis on CPU speed.
Any machine based on the Intel Pentium III or the AMD K-3 will be more than adequate for a real estate agent. Unless you plan on playing the latest high graphic games or doing cad-cam engineering on the side, don't worry too much about CPU speed. Memory RAM, or Random Access Memory, enables the CPU to work on programs in a very fast atmosphere. You want a system with at least 64 megabytes. If the unit you like comes with less, then you can simply buy an additional memory as needed.