Generally renting from an Owner requires less paperwork and it will probably get you a unit in a nicer part of the complex, the lower prices of the Concord/Developer units give renters a savings and almost a half price Security Deposit making it cheaper for renters to go with the developer units.
The office has assisted owners in renting out their units, but their main interest is in getting the developer units rented and at the lower Concord prices/deposits those obviously fill up first. Below are links to various Concord sites including one with their 'Resident Handbook'.
Can an owner rent out their units? Sure they can, but probably not until the Concord units are full and if they go head to head in pricing it might be difficult to break even. Owners renting out their units might mean taking a loss every month depending on what their monthly mortgage payment is.
For prices see Concord at: http://tinyurl.com/3tmf5gl
See the 17 page