Before we get too ahead of ourselves, I'll give you some tips on checking out the washer before purchasing. We don't want you getting something that has been abused, neglected, a rust bucket (happens where these are located in a damp basement) or worn out to the point where it requires too much work and money to fix.
1. Check the condition of the inner the tub. Make sure there's no chunks of missing porcelain or rust spots in the tub. If the porcelain is worn thin at the bottom, the machine has seen a ton of use/abuse and isn't worth purchasing.
2. Shift the inner tub around in all directions checking for lack of movement and any sounds like squeaks or metal-to-metal contact. What you are checking is for worn damper pads. There are 3 glued pads located at the center of the base lubricated with silicone grease that the whole mechanism pivots on. These pads need to be lubricated every 20 years or so (sooner if it's used more, such as a large family like yours). If these get too dry, friction will cause the pads to be ripped off from the base during the spin cycle and then the aluminum damper dome above gets gouged up by the metal base dome below. The aluminum damper dome has been discontinued for over a decade and is difficult to find in good used condition now.
3. Bring a small stubby Phillip screw driver and remove the front cover. There are 2 Phillip head screws located under the lip near the bottom of the front panel about 1 inch away from the corner. Remove these 2 screws at both ends and lift the front panel straight out 90 degrees. Doing so unlocks the clips at the top of the panel and the panel can be removed. This can been seen at this clip from 0:57-1:33
Look around at the interior. If there's any signs of rust, particularly at the base, that isn't very minor, walk away. Look for leaks around the outer tub (triangular tub cover seal area), in the front left corner where the bleach cup is located, left side of the machine where the water injector assembly is located, and left back area where the water valve is located. Check for signs of leakage under the outer tub where the transmission is located. Any leaks here indicates the need for a stem and boot seal replacement. When it gets bad, it will throw black gunkyness on the sides of the cabinet inline with the bottom of the outer tub. Check for leaks around the water pump where the hoses go. Generally any leaks here are just a loose hose clamp.
Check the damper pads as described above at the center of the base. Check around that all 3 pads are in place and not missing or sneaking out from under the damper dome area. If you find the damper pads missing or black aluminum dust around the damper, walk away. You can see a stray damper pad and the black dust around the damper assembly in this thread at Reply #15
https://www.automaticwasher.org/cgi-bin/TD/TD-VIEWTHREAD.cgi?36743
4. Tip the machine back and look for leaks under the center pulley. There's a lip seal at the bottom of the transmission on this model (the seal is in a different, much harder to replace area in the 1956-June 1986 machines) that can leak overtime. The seal it cheap and easy to replace though. You can use this leak as leverage for a cheaper price.
Plug it in and at least check the spin cycle. With an empty tub, the machine should be up to full speed in less than a minute. Any strange sounds during the spin cycle indicate a worn tub bearing, worn or missing damper pad(s), or loose tub to suspension brace bolts (generally a knocking sound).
5. Take a look at the water valve screens at the back of the machine. If the screens are plugged with any amount of deposits, factor on replacing the entire water valve. Talk the seller down on the price if the screens are plugged.
If that all checks out, you should be good to go.
If you're looking at purchasing the dryer, I can give you some tips on that as well.
