Members' site in Craft possible out of the box?
Yes:


In Craft, all Elements — including Users — can have custom fields of their own. (So, for example, each User could have a "Bio" field.) You can use a User Profile Form to allow Users to edit their own profiles.
You can restrict the upload directory for each Assets field. So, for example, you could create an Assets field that stores files in a directory based on each User's ID, which would effectively keep one User from viewing/disturbing another User's files.