The best information for you would depend on the kind of condiminium (price range, target market) and the location. Also on whether you need the information to be in English or Spanish.
A great starting place would be the "State of the Nation" report
www.estadonacion.or.cr This is a report on Costa Rica's development and offers reliable statistical information. There is an English summary- report here.
Indicators and democratic governance: Measuring Sustainable Human Development in Costa Rica The
Chamber of Construction Keeps statistics on building starts as well.
These are good sources for nationwide statistics, however if you are interested in a particular area then your best source would be a realtor who has covered that area for the last 5 years or more. You can contact AE members here:
Costa Rica AE real estate agents. You can also see
44 Townhouse Style Condominiums or
32 Apartment Style Condominiumsor
10 Beach Condos