Lets say a wealthy man wants to build a house. Was there anyway he could buy a slave for the short period of time he needed? Did any slave owners offer their slaves up for work or were they already to busy doing other things?
Yes, slave owners did rent out their slaves to others. Ron Chernow discusses this practice in Washington: A Life, describing how George Washington sometimes rented some of his slaves out to nearby plantations, especially ones skilled in things like carpentry.