Amos and Betty each own an undivided one-half interest in a tract of raw land. They construct an indoor skydiving facility on the land, which they lease to Constance for $2,000 a month, the profit from which Amos and Betty share equally. Constance operates a indoor sky jumping business on the site. What is the tax classification of Amos and Betty's relationship? Would your answer change if Amos and Betty later tore down the skydiving facility and constructed an apartment building on their land, which they then leased to tenants through an agent, who also provided customary services such as security and parking to the tenants? How about if Amos and Betty then built a yoga studio and meditation room in their apartment building and then charged the tenants an extra fee to use those facilities? What if no extra fee was charged?