I lived in and traveled in a Chevy Astro Van for about 9 months a couple years ago. The main thing you need living in a van is a power source which ideally is something like a solar panel with a battery bank and inverter. You're not going to be running your van all the time but likely are going to want either a fan blowing or access to charging phones and other devices even when your van isn't running so you need solar and a batter bank to store that power to be used later. That's really the main need in a van. There's other things that can be helpful like a composting toilet or at least a 5 gallon bucket for emergencies but power is the biggest thing to me.