97 Jeep w/Noise when put in 4 wheel drive

Something is wrong :0

That's about the best you can do with the info provided. It could be an operator error (don't use 4wd on hard surfaces or it will bind), a simple adjustment to the shift linkage, a bad U-joint, a trashed trasfer case, a bad front diff, or several other common maladies.

A rebuilt transfer case, rebuilt front diff, and 4 new U-joints including labor might run a couple grand. Offer two grand less than the going market rate and you should be in good shape.

Pers> I have found a great deal on a 97 Jeep....the owner claims that when

Transfer case, front driveshaft, front axle. Some gear noise when engaged is normal, a little more in low range. Clanging, banging, scraping noises are not normal. If the owner drove it on pavement with the transfer case engaged, some noise would have been the least of his problems.