Just sit back and think of how you are going to use it and what you will need to fit to live like that.Then everything else is a compromise.You have to find the best vehicle base for your purpose,chassis length etc,or van space.Then rough draw a plan of how you can get what you need into it,taking a lot of time and not being afraid to scrap the plan and start again,usual items are,toilet(what type and size) cooking facilities,gas or oil or electric or solid fuel.Heating-the same.lighting ? storage ?water,fuel,waste water tankage and pipework ,sleeping arrangements.security etc etc,the list is only governed by your budget.You will enjoy it immensely and never look back,i did thousands of miles using a camper van,i never stayed anywhere long.good luck with it.
