Maintenance for an idle bicycle kept indoors?
A lightly-used bike stored indoors in a dry (not humid) environment does not need much special maintenance. Just keep it clean with light lubrication on the chain.

The tires will slowly lose pressure. A bike left sitting for a long time on one spot on un-inflated tires is probably not good for the tires or tubes. Keep some air pressure in the tires or hang the bike up off the floor if you can.