You could change his business to be modernized and sneak in some software development into it at some point? :) Just be wise about it, don't just break his company for yours haha, you might even learn a lot for your own business from and he could fund you once he sees how genuine your work is. Worse case you go back to programming with new business knowledge. Who knows you might even meet business minded people your age who could benefit your startups? Take a leap and if you don't like it after sometime, just plan to leave or reasses.