i dont have any suggestions for you for under $500 for 4 cams and a DVR that arent your typical "costco" type packages, but i just wanted to answer your question:
Quote:
"do the cameras have motion detectors and do not capture images unless there is motion, or do the cameras send continuous feed and the DVR selectively records based on whether the image changes ?"
the camera sends constant video to the DVR. the DVR will have an on screen setup menu that will allow you to choose motion recording on that channel, and the DVR is what detects the motion and decides to record.
i think you could get into a decent DVR for $300-$400, esp if you only want 4 channels, and dont need remote viewing. I've seen some cost effective stuff from avtech and such. the dvr is the heart of your system. before choosing any cams id search out and buy a nice DVR within your budget, with the options you desire most, and with good recording quality. the record quality is important since you want to be able to give this to the police and identify her face. i dont think a budget DVR will have good recording/compression quality that fits into your $500 budget with the cameras. you may have to stretch your budget a few hundred dollars IF you want a DVR with good recording quality. For what you described to us for your needs, if it were me, i would want something with at least 4CIF (as opposed to CIF or 2CIF).
that said, there are a lot of entry level systems in that price range that are def worth a look.
its been said here a million times, you get what you pay for!
also, i wouldnt totally rule out wired cameras, either. do you have a lockable closet in your garage that you might be able to put the DVR in? or, what about above the garage? is there a room, maybe an office on the second floor that is located directly above the garage where you could run the wires through the garage ceiling and into the office? or, maybe an office next to the garage where we can fish the wires?
good luck with catching the suspect!