I think the estimated age of the Sun is about 10 billion years in total. It is now around 4,6 billion years (the same as the Earth). It will eventually start to shine brighter, perhaps as soon as a billion years or two, and thensubsequently start growing, but this is a slow process that will take a very long time. It probably won't become a red giant for another 6 billion years or so, but Earth would be uninhabitable long before that time.
Here is a simple overview which was used for a university lecture:
http://www-astronomy.mps.ohio-state..../vistas97.html
It is outdated now and may be inncorrect, though.
