When you are looking to  purchase a multi-unit property or an investment property in which you plan to rent either units or the entire property itself, having a clear understanding of what the rents are most likely to be is key to determining what the property should be worth to you as an investor (and understanding the actual cap rate for the property).  Here in the greater Oakland, Piedmont and East Bay area, you can see drastic value swings depending on location, building, etc.  Now a website caller RentoMeter can give you a much better understanding of area rents by simple entering some basic data on the property you are interested in learning more about. It will use real market data collected on area rents to give you a value range.  The site can also be used in reverse for renters wanting to see if a property they are considering renting is being offered at a reasonable market rate.