Well if they say yes try to find out what history they know of the pony. Many ponies that I deal with we don't know the history of so we begin. . .
1. Take a halter and lead rope and walk over to the pony. If the pony stands then good. If the pony runs a way. Stand and wait for the pony to come to you.
2. Put the halter and lead rope on. If the pony is willing to follow you, then it probably is halter broke. If it starts freaking/spazzing then its not halter broke ha ha ha
3. Tie the pony and take a body brush out. Let the pony smell the brush and then start brushing. If the pony is fine (can do a little dancing) then it doesn't mined being groomed. If it tries to kick you then don't move on. This means you need to work on grooming and ground manners
4. If you can pick the pony's feet and brush it then take a saddle pad and put it on the pony. If they pony allows this praise it. If it doesn't let the pony smell the saddle pad and rub it against him/her. If they don't let you do this then don't move on to the saddle
5. If you can get a saddle pad on then put the saddle on. If the pony doesnt allow this then you will need to work with tacking up. (pony probably isn't broke)
6. If you can get a grith on and a bridle then the pony has been handled before, but don't get to excited because it may have never allowed someone on his/her back.
7. Lunge the pony on lunge line and watch how it reacts. If it tries everything to get the saddle off then its not broke. If its perfectly fine you may be lucky
8. Attempt to get on the pony and go from there ..........
If you get this far than let us know so we can give you some more advice.
I hope this helps