Is sharecropping a good piece of outside evidence?
it can be used to prove that the end of slavery did not help African Americans as much as the North hoped for as sharecropping is still a form of slavery
How does it connect and differ form tennment farming?
Sharecropping would work as outside evidence as long as it isn’t mentioned in the document or the source(obviously), but since sharecropping happened throughout US History, I would recommend going deeper into the specific historical context that applies at the time period of the DBQ.
For example, if it’s a Reconstruction DBQ, you could talk about how recently freed black slaves and poor whites(yeomen) worked on other people’s land for little pay, and for blacks, how it’s not much of an improvement from slavery.