Documents to be aware of when buying a Property in Portugal

Only with a Golden Visa and the property must meet certain conditions/values:

https://imigrante.sef.pt/en/solicitar/residir/art90-a/

Well, any resident visa will require existing accommodations.  If you own a property you could live in, then that fulfills this requirement.  Probably most people get there by signing up a rental instead.

If you want to pursue this, you should speak with a lawyer who can handle immigration and real estate.  A lawyer will be a very big help for the former, and practically required for the latter.  Some people go through this on their own, but it's a big risk.  JohnnyPT is a very comprehensive resource, but he can't really see through the questions you're asking, and take stock of your situation and give you the right advice, the way a lawyer could.