In need of guides to maintain the bike that I'm about to get
Link-only answers are frowned upon here but I'm going to provide one anyway
https://www.parktool.com/blog/repair-help
Park Tool Company's Repair Help web site is the most comprehensive, professional and understandable set of articles and videos on bike repair and maintenance that is out there.
If you run into specific problems, Bicycles Stack Exchange is of course a great resource.