I do not recommend this, though I have seen it done.
1. Find a beater that is not livable / barely livable.
2. Move in <-- I know not the smartest move.
3. Contact owner and offer to fix it for free rent - they buy materials.
4. Save rent money for down on next deal that is yours.
I have built homes in some rough areas. This is a standard maneuver for characters that live in these areas. I say "characters" because, well, if you have spent much time in these types of areas you know what I am talking about.
You could of course offer to fix it without moving in first, which is more advisable, but not always done, for obvious leverage reasons.
Anyhow, you are taking a situation where the owner has an unusable asset and making it usuable. You then move out when it is fixed and the landlord has gained and you have had free rent along with saving the 12% HML interest you were planning to pay. Believe it or not I have seen this type of situation develop into a good relationship with the owner where he moves you to another house that needs work and suddenly you become "his guy" for better or worse.
Anyhow it does happen.
Just for the record, I do not endorse this, but I have seen it work out in more than one instance.