Some wonderful tools that would help are Trim, Extend, and Corner tools.

Trim allows you to stop a line at another line. So if you drew a + you could trim the top to the - and make a T.

Extend does the opposite. It makes a line longer until it hits a target line. It turns |- into a T (rotated).

Corner tool trims or extends two lines as need to make a corner. |- becomes L by clicking both lines.

Look to AutoCad or Revit for examples.