Not in the USA because to be a slave you had to have black blood in your system which means that if you had black blood in your system you were not considered human but cattle and therefore a slave. However outside America there were plenty of black slave traders. And black tribesmen involved in selling other black people into slavery. The whites were the end users; the blacks and the Arabs were the suppliers.
This is not true at all. William Ellison was a Black slave owner in South Carolina and the majority of slave owners in New Orleans were Black. William Ellison, whose slave name was April, became a slave magnate and expanded his business throughout the south, from South Carolina to the Mississippi River. I would strongly suggest you Google "Black Slave Owners" and I guarantee that you will have a plethora of information.
so that they can help them in manual work
To be killed, betrayed, or sold by their owners.
because they were stupid
It was because the people of Africa were strong and beautiful. The traders saw them and thought they would be better slaves and easy labor to get. Some also believed that they were giving the black slaves a better life in a colonized world and giving them religion and a chance and "life". It is also said that some of the slave owners quoted, "Once a black man, always a black man. You can never lose a black slave."
because they would run away or not do all their work.
black will rebel
No
If you are referring to the American slave trade, the slave traders were mostly Dutch (Caucasian) but there were also black slave traders and slave owners. The most notable of them was a Virginian by the name of Anthony Johnson.
From the Scottish plantation (and slave) owners.
Slaves could not be married to their owners, for their owners were most likely white. Back during the Civil War; and before then, it was not necessarily a law, but un-allowed for a black man to marry a white woman, or a black woman to marry a white man. I believe, to marry a white woman or man and be black, I think you must be an ex- slave. You can't be a slave if you marry a slave owner.
Slave owners are people who own the rights of the labor of another person, and can hold total dominion over their lives. There were slave owners all across the globe and in all ages of human history. Slave owners were Black, White, Asian, Native American, Arab, etc...All races have been slaves and slave owners.
the white men benifitted, slave owners
Slave rebellions.
Masters or just plain slave owners
North Slave owners did pay their slaves, but south slave owners didn't. See the following link.
The slave owners bought their slaves at auctions.
Because the slave owners didn't have to pay for the free labour the slave were giving them.