I had a Belarus 420AN for about 5 years. It had a bushhog front end loader that was worth more than the tractor. Without a doubt, the tractor was not very refined, but it was a powerful, heavy piece of equipment. It was a 57hp air cooled (noisy-very noisy) unit, but it could flat out pull a disk/plow, etc. My main problems were electrical (starting and charging). Once I changed the alternator to a GM/Delco, replaced the starter circuit with parts from Autozone, etc., I had very few problems. I did have a hydraulic line that was right below the steering column that busted a few times - I got OEM replacement and it leaked as soon as I installed it. I sent it back and had a set of hoses made locally. I eventually sold it locally and bought a new Kioti DK 45 and I'm not sorry one bit. I can't say as I miss the Belarus, and I wouldn't really want another one, but if a screamin' deal came along, I might not be able to resist.
The long and the short of my recommendation would be buy one only if you feel like tinkering on it with little support, improvising new parts, don't need it to run on a reliable basis, and can buy it for a song. The Belarus machines have their places, but they are kind of rare.
Good luck.