I use crashplan and just charge for my time. Most small offices can get by with the $120 a year option, which I believe is up to 5 machines unlimited. It also gives them remote access to files and does revisioning and such. It also includes a LAN or local backup option which I dump to an attached external drive. Then I use AOMEI, which is free, to do weekly images, which are included in both backups, three deep each because why not.
When your niche is NPO agencies, you have to do what you can to save money.
I also then sell my RMM of choice which is currently CentraStage on a yearly service plan. That lets me remote in whenever and also lets me automate things like disk error detection and such.
Edit: if your small office has more than 5 machines but not enough to warrant the next price jump, you just use the crashplan agent to dump to a lan share on one of the machines that backs up to cloud, and then include that folder in that machines cloud backup.
I have a few clients on pure S3 backup as well. Much less user friendly, but stupid cheap and reliable.
With Dropbox pro now giving a terabyte for $100 a year, and drive offering something similar with a base of 25 gigs, you can use any of half a dozen local apps to back up there too, including crashplan without a subscription.