If you're a landlord whose rentals lose money, it may mean a lot if you qualify as a real estate professional for tax purposes. Nothing illustrates this fact of life better than a brand-new case handed down from the U.S. Tax Court involving Najeem and Olubunmi Adeyemo, a married couple who owned seven rental properties in Maryland. During the housing downturn, the Adeyemos experienced difficulty renting out their properties and collecting rent from tenants. As a result, they incurred substantial losses: $171,651 in 2008 and $96,806 in 2009. Fortunately, they did have other income: Mrs. Adeyemo worked full time as a pharmacist, and Mr. Adeyemo worked in pharmaceutical sales. Their joint wage income was $232,992 in 2008 and $175,354 in 2009. So, the Adeyemos had big rental losses...