Probate records for individuals from Lebanon who died from 1900 to present are at the Grafton County Courthouse in the Probate Court office.
https://www.courts.nh.gov/our-courts/circuit-court/probate-division
Probate records before 1900 were sent to the State Archives, 71 South Fruit Street, Concord, NH.
State and Provincial Papers may also provide some useful information.
https://scholars.unh.edu/propapers/
Eighteenth and nineteenth century probate records from Grafton County largely concern people who owned real estate at the time of their death. Older individuals often sold their land or gave it to one or more of their children. In such cases, even though the individual may have been well off in previous eras, they may not have an estate that was probated.
A number of early Grafton County residents disposed of their lands with conditional deeds to one or another of their children. If you find no probate records for someone who owned real estate, check the land records to be sure that there is no conditional deed that disposed of the land provided the child looked after the parents during their lifetimes.
Lebanon Historical Society 