Are transimission problems on 125k common

I am considering purchasing a 98 basic carvan w/ 125k on it.

From my research I understand this mileage point to me a great time for the transmission to go out.

Is this true and what are some procedure you can take to detour this problem?

I can speak from experience, I had a 97 T&C and the transmission went out at 131K. I didn't abuse it and had the fluid changed regularly. If this is the original trans you may go for another 100K but it could crap out tomorrow. Use caution with your purchase. Replacement/rebuild from AAMCO will cost you $1700 if it goes out.