I'm looking to get a used upright piano for the little ones to play/learn and could use any advice as I have no clue on what's good or bad.  
I'm looking for something under $1000. (I don't mind buying the piano below (as long as it works) & having it re-done) 
 
I found this piano in a local ad, but don't know if it's worth re-finishing or what other details are involved in fixing it, but this is the description on the ad:
 
"I have this POS 1948 Lindenman & Sons piano sitting in my garage that I am looking to get rid of. Someone please make me an offer and get it out of here. Will take anything."


 
  
  
  
  
    
    
   

Ouch, if its been in a garage, with ever changing air temperature and humidity that could be trouble.

Parts could tend to dry out, break, etc.  The only way to know would be to try it.  What sort of condition are the felts and hammers in?

Another thing to watch out for is the condition of the frame.  In some older pianos that have gone way flat, and suffer from a weakened frame, tuning back up to concert pitch becomes impossible, as the weakened frame cannot handle the additional tension from all the strings at true concert pitch.

If it needs extensive restoration to be playable, that can get very expensive in a hurry.

As there are several different sizes of upright pianos, in general, the taller the height of the upright, the better the sound will be (due to longer string length).
<edit> Given the description of the piano as "stinky" I would likely take a pass on it.  A piano needs stable room conditions, and decent care, or at least something better than neglect.  The odds of it being in really playable condition are not good.
 
Note that I know just enough about pianos to be somewhat dangerous.

Just take my piano, Mesh! It's just like an upright - only lying horizontal on three legs. The blue book price is around $10,000 but I'll let you have it for half that because you're a friend of bapu's.

Temps & humidity will screw one up in a hurry. I went looking for a piano many years ago. I looked at one that the lady had kept in her shed. Heat & humidity & cold in NC had ruined it. Keys were sticking bad. The wood had swollen and parts were no longer in alignment.

I found an old one in a church that was getting rid of a number of uprights in their children's building. All the keys worked. It had a horrid paint job and it was mine for $125.

I got it home and started stripping the paint. I discovered that there were several types of wood in it so I opted to paint it glossy black and tune it up. Using my strobe and a socket wrench that fit the tuning pegs, I got it up and running in fine fashion.

I kept it for a few years and sold it for more then I paid.

My advice... play it, and be sure all the keys work freely, and the pedals all work too. No sticking keys and no funny sounds inside. Look inside.  Make a lowball offer...after all... you gotta move it, and make repairs to it so get it for a good price.

You need to get in there with a tuner and see what pitch it is at or how close to concert pitch it is. That is going to be a biggie for you. Watch out if it is well down from concert eg semitone or tone. You will  have a very difficult time getting it back up to concert pitch and it might come back with work or it may not.  A piano that is not on pitch is pretty useless!

Tuning a piano correctly is a process. I have known several people who tuned piano's for a living or a sideline.

A piano that is out of tune should be tuned 3 times over a period of 6 to 8 months. Bring it up a bit each time depending on how bad it's out.

A piano should be tuned every time it is moved physically.

You should tune it as often as you have your teeth cleaned..... hopefully on a 6 month basis.... but just like teeth, some never get that professional touch as often as they should. I'm thinking probably only professional players and piano's in concert halls get that sort of treatment. The concert hall piano's & studio piano's probably get tuned more often than that.

If it doesn't play well and FEEL good, then I wouldn't buy it.  Those are no fun to play, even if they're just for the kids.  (those kids grow up and may appreciate a good piano.)  :)

As much as I love real pianos (good ones, that is), have you considered an electric keyboard?  They're way better and cheaper than they used to be.  Good enough for kids to learn on.

AND they can put on the headphones when it starts to drive you crazy.  :)

+1 on what Janet said.

Following up on Janet's post.

The weighted key midi piano's with full sized keys would be the answer in my book.  They are smaller, and lighter, and don't need tuning like a real one will. In addition, you will appreciate the headphone jack when it's time for the kids to practice.

You can pick up a decent one for less than a good "real" piano in top shape, or buy a used midi keyboard that is top of the line for about the same.  Some of them are built to resemble real piano's if you want the look.

Yup. look at this