If you're below 30 you'll get social housing immediately after being "stuck" in private rental for 2 years - which, considering the heavy rent price restrictions of the MRG - is more than cheap in Vienna. You'd have to pay the mark-up of "Direktvergabeablöse" (one-time payment of ~3-4k€) if you want anything decent, of course.
If you are older than 30 and earn enough to be disqualified from social housing, you should have enough equity to satisfy any property loan already.
If you are older than 30 and earn enough to be disqualified from social housing, you should have enough equity to satisfy any property loan already.