630A was a good model in its day, I had 2 of them, reliable wisconsin engines, simple to operate, and capable of grinding most stumps. Now for the bad news, tow behind design makes it difficult to reach a lot of backyard stumps, you can use it off the truck by staking the tongue it but it is a PIA to do. They cut very slow compared to todays higher HP models and todays self propelled models makes backyard work so much easier. As for cost I have seen them sell used for $1K up to 3K which for that $$$ you can get a decent self propelled to start grinding with. If you are looking at one with a good wisconsin engine the motor is what a lot of folks are looking for since parts for the older ones are getting hard to find. Do a site search and type in 630A and you will get a lot more info.