This depends on your goals, the area, the market, etc. Many people hold the real estate until they double in value. Others hold them until the mortgage is paid off. Still others hold them for a specified period such as 7 or 10 years.
Some investors don t sell at all unless the neighborhood peaks out and values start to go down.
You would be smart to monitor Chicago real estate values on a consistent basis. This is not to say you should panic and sell every time there is a little glitch in the market. But if the area has started going down while other areas are going up, you may want to sell and do a 1031 tax free exchange into a property that is appreciating better. They can then sell them by taking a down payment and carrying the mortgage themselves. This can provide them with a good, stable cash flow for many years.