Real estate investing involves the purchase, ownership, management, an/or sale of real estate for profit. Improvement of real property as part of a real estate investment strategy is generally considered to be a sub-specialty of real estate investing called real estate development. Real estate is an expensive, non-liquid asset, and therefore real estate investment activity is capital intensive, risky, and cash flow dependent. The primary mode of business failure for real estate investors is an inability to remain cash solvent.