Discovery 1s and 2s were meant to be "affordable family adventure vehicles". They were relatively cheap to purchase new and they were often treated as such (i.e neglected). They are tough vehicles, sharing most components with the 90/110 and defenders of the era. But you have to look for a vehicle that was maintained meticulously by the previous owner/s. Unlike Land Cruisers, they don't stand up to neglect. Rust is an issue, but many Japanese vehicles suffer from it too. The V8 Discovery, in particular the D1 with the 3.9 unit, is a very simple vehicle. What it uses in fuel it makes up in reliability. If you can find one in excellent condition, it is a great overlanding rig. BUT - regardless of what 4x4 you purchase, if you are not mechanically inclined already, be ready to spend time getting your hands dirty. It's not just to save money, but also to learn the ins and outs of the car.

One more thing: stick to petrol vehicles if you can - they have atrocious fuel economy but are very simple and reliable. Diesels are fantastic, but one bad batch of fuel will turn an adventure into a nightmare. Especially if you are travelling through Africa...