There are many different sizes of squeegee, not to mention a multitude of brands, materials, etc.
While the vast majority of window tools work together with tools from other manufacturers, there are companies that produce tools that only mate with their own brand (for example, replacement squeegee rubber that only fits their squeegees). While some of these systems are great, if you start with these brands, be prepared to stick with them alone for the rest of your window cleaning days.
Regardless of the brand of squeegee you purchase and whether you plan to use it a couple of times per year on your home or every day for years to come, purchase replacement rubber blades right up front. These are simple and necessary to replace often. It takes only one tiny nick in the rubber to render the whole tool useless as it will leave streaks no matter how good your technique.
Choose a moderately sized tool and go larger or smaller in the future to meet your needs.