If the TiVo you get is new, you'll have a week of free service in which you can run the Guided Setup, and get your local lineup. Otherwise, if you don't pay, you can do a channel scan, but it won't have the correct call letters/network logos for your channels. You won't be able to make recordings either, though live "trick play" (pause, rewind/FF through live buffer) should work. Of course, Netflix, Amazon VoD, YouTube, etc., and streaming/downloads from a PC won't work either. Basic tuning and trick play functionality will be all you'll get.
Also, keep in mind that the clock is set through the TiVo service, so the clock will probably not be correct either.