Keep is a good word (not least because it gives me another chance to post a photo of a castle - do you know which one?)
It means to continue to have something, to save something for future use, store in a regular place (we keep The Sphere in the garage), continue in a particular position or activity (she kept her head down) or to remain in good condition (fresh bread doesn't keep very long). It can also mean to do something you promised to do (I keep my promises) to provide accommodation and food - or the money for those things (he earns his keep)
If you have a friend with enough money you could be a kept woman. You might want to keep up to date, or with the Jones'. Or perhaps you'll attend keep fit classes (which generally means get slightly less unfit rather to maintain an existing state of fitness in my experience) and of course it's the strongest part of a castle.
Not bad for just four letters, eh?