newcontractor

I am starting to work with my dad. He runs his own HVAC business in Georgia. I have to start investing in tools and not sure where to start. I know what hand tools I want, but not what power tools. I am trying to see what other guys use, but it is just such a wide range as they have built their line up over years. My dad is just set in his ways and still uses older tools. I want the best tools for the money, which I am sure everyone does. I really want to stick with one brand because i don't want to have a lot of different batteries. I heard the Lithium batteries have a hard time in the cold. I am in the south, so i am not worried about that. Any thoughts or help.