The problem with a lot of these cars like KE70 is back when they were new they new they were seen as just a commute /family car, which in essence it's raison d' etre.
So no one took extra care of these cars. They were used as daily cars, left out in the sun and the rain. Over decades, the drain channels clog up from dirt and leaves getting stuck in them, the sunlight and heat repeatedly baking and drying up the seals around the glass and windows, letting water seep in the cabin, rusting out the floors and spare wheel well, boot lid rots, and the lower fenders and door rust starts eating through.
Its only like 2 to 3 decades later suddenly the retro bug started hitting the motoring population and suddenly we see IG builds with trendy JDM yo style pics and videos, of shiny stanced out examples. However, the repairs done are usually shoddy and consists of heavy layers of bondo slapped and smoothened over the rusted out areas and then painted over. While what you see on the outside might look nice, If you know where and how to look for shoddy repairs, you will know the work done was just patchwork.
My advice is, if its primarily a play car, and you dont want to pay much for it, you may just have to take one of those rust bucket types and perhaps just take steps to slow down or prevent further rot. When the time comes to sell, there will be plenty of other buyers willing to take it off your hands for probably the same price you bought it for.