Welcome, Brooke.
It sounds more like a future remediation site than a forest garden. I would give it a hard pass.
A municipality out where my much better half works had to buy out a local farmer after their unlined, uncapped, active landfill was proved to have started leaching into the groundwater; his land was directly downplume, and also happened to be where all the airborne litter would blow.
There might be a niche here and in similar situations for a biological remediation company that can produce lumber, paper, textile, or fuel biomass as a saleable by-product of legitimate biological remediation and reclamation, starting from the microbiome up with
compost extracts and fungal slurries. One might not naturally connect remediation and a woodlot coppiced regularly for firewood, or one grown up in textile and paper plants, but if those plants are either sequestering contaminants, or providing the soil environment and inputs necessary for healthy bacterial and fungal interactions to break them down, then removal for sequestration in the form of durable goods or combustion for heat in effect removes those contaminants from the soil.
But unless you're in the position to profit from seven acres you can manage as a woodlot, or some other forest product business that doesn't produce food, and unless there are a tonne of grants and subsidies that will help you get there so you can also buy a place to live and grow food you actually want to eat, I would keep looking.
Good luck, though, and keep us posted.
-CK
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
-Robert A. Heinlein