Honestly, I don't think you'll get that much business. You're not doing something that most people aren't willing to do on their own, which is plan which park on which day and calling WDW Dining for advance reservations. A lot of travel agencies are also willing to do this type of detailed planning for free when they book their vacation through the agency, and anyone looking to save time likely used a
travel agent to begin with. Your friends and family know you and trust your advice, and you're also doing it for free. I bet if you charged them for it, they'd very nicely tell you no thanks and then figure it out themselves.
If you really want to do it, in your shoes I'd try it with little to no start up costs, you never know...it might be worth a shot. But I wouldn't sink much money into it until you get a better feel for how much business you'll get.