thesmallpastry

I am a professional baker with a small business. Recently a friend also with a business asked me if I can bake for him, doing prep work i.e. Mixing, scooping, storing cookies, Mixing cakes and freezing, Baking Pie shell, Mixing frostings ect... I am wondering what would be the best approach to charging him for the work I provide. hourly or by piece.. Is wholesale an option? Should I use my ingredients and his recipe and charge for a normal whole sale account? Thoughts, Thanks.