Making a Topo map

Hey all I’m trying to develop plan and map of a sustainable agroforestry system 45mins north of Ann Arbor Michigan. I am trying to come up with a plan and map so that I can sell the idea to my parents that will moving to the property in a few years. It’s my grandparents property and it’s beautiful with varying hilly terrain and slopes down to the shallower part of a small finger lake on the northern property boundary. On the western property boundary there’s a narrow wetland with cattails and tamarack trees that stretches from the road in the south all the way towards the lake in the north. I have a general sense for the topography of the land and it’s different habitats but I’d like to map out the micro topography in more detail so that I can incorporate it into a more comprehensive map so that I can more easily convince my parents to implement some sort of sustainable agro-forestry system there. I would greatly appreciate any advice anyone has to offer the property is about 20 acres. I was just thinking how awesome it would be to have an app on my phone I could just open up and slip in my pocket and then just walk across the property over the course of a day or two all while it’s recording elevation data that I could then use to make mthe topo map, so if anything like that exists I’d be eternally grateful for some enlightenment. Thanks!