Hey Justin,
I wouldn't offer them parts and labour if that's what your asking. DVR's ect ir's and even decent cameras can cost, and may cost you.
I offer the customer whatever warranty I get. Basically the contract states they get 12 months warranty. HOWEVER, if they have faulty item which I get 3 years warranty on I wouldn't charge them for replacement, even though it goes against their 12 month warranty, you'll find it gives you a better name.
I'd give the lenses and housings a clean, if your into vcr's and know your stuff I'd give the tape rollers, and so on a clean, aeroduster and pcb cleaner etc etc. Check psu's for voltage and current readings to make sure everthing a ok, check the fixings of the cameras, time and date on vcr almost always needs changing, give the monitor screen a good wipe, you'd be supprised how dirty these things get, it also makes a difference to the quality of the pictures!!!!
Any parts I'd get them to pay for extra obviously. My cctv contract is the same as intruder basically with a few minor alterations, I'm sure you could do the same. Some samples are avalible, if you goto ssaib there's a link to ecs-service, I think it's www.ecs-services.co.uk but don't hold me to it. They have all the forms you'll probabally need.
Regards Tony.