A Feasibility Study is a determination of the likelihood that a property developement will fulfill the objectives of a paticular investor.
* Estimate the demand for housing units in the area.
* Estimate the Absorption Rate for the project.
* Discuss legal and other considerations.
* Forcast Cash Flows.
* Approximate investment returns likely to be produced.
So to answer your question, Commercial as well as Residential can both be very profitable. So much depends on Supply and Demand and 'Location, Location, Location!
You can take classes to learn about residential investments as well as commercial investments.
If sims urban oasis you are just staring out, I suggest you take classes in residential investments first. There is much more to learn in Commercial Investments.
You can start out by "Flipping Houses" a term used in buyiny and http://har.com/ fixing up run down http://www.trulia.com/ properties and then selling them for a profit.
If you are interested in the real estate market, then start by finding a Residential Investors Seminar in your area.