There are factors that will effect this answer. What model the tractor is, what engine it has, what transmission, what condition, where it is being sold, what time of year it is being sold etc...
Right now, a typical Craftsman L-1000 in that year range and in good shape will sell for around 300-350 here in Cincinnati, Ohio.
Husqvarna
A person can get an owner's manual for a Craftsman lawn tractor by contacting the Craftsman company. The phone for customer service is 1-888-331-4569.
1997
MTD
1997
2006
Try searspartsdirect.com
Gates
it should be under the seat.
March 01 2004
You can get that from Sears' online parts directory.
Check your chair switch!