I bought a relatively inexpensive one ($80) in the sporting goods department at Wal-Mart a couple years ago and aimed it at a pile of scraps. I got a cat, a couple of possums and a rabbit. lol It was a little bit complicated to set it up but nothing I couldn't figure out with the manual. It wasn't digital, so I had to take in the film to see what we took pictures of.
If you're trying to catch people(prowlers), you would definitely need the infra-red. I suppose the flash might temporarily scare off some animals so if you're wanting them to stay around, you could invest in the infra-red.

Here is a link that might be useful: Bass Pro

I bought hubby one for Christmas.didnt use it yet....same here alot going on.Not all animals,neighbor kids too.Theyre chasing our longhorns they think theyll charge......

I got one for Christmas about 4 years ago, and in fact I do believe I posted a few pics form it here-er, had HELP from SOMEONE ELSE in posting pics here. I'll never learn how.
Anyway, there are all kinds of options to consider, and I'd do a little research before you buy. I got mine from Cabela's and had fairly decent luck with it. It all depends on your ability to scout a likely traffic area, get it set up and rigged correctly, and not screwing up the film, if you get one that relies on standard film.
Oh and most importantly...if you get the infra-red sensor, follow the directions about avoiding the sun. I got a most wonderful roll of film back....24 exposures of a sunrise, taken at 4 pics every 15 seconds. As long as there is heat or motion, the thing will continue to go off for whatever intervals you program.