With that out of the way, I think that <$100 total cash flow for a duplex is a little bit to slim of a margin.

Slim.

The chances are so slim, why worry about them.

However, it occurred to me that once you reach a certain number of properties then the standard amounts don't apply. ( 3-10% vacancy, 5-15% repairs Etc ) For instance if we own 10 properties then the chances that all of them will be vacant at the same time would be slim.

REI is like anything else in life IMO there are no magic pills & no shortcuts there is success to be had and wealth to be built but it typically doesn't happen overnight and isn't sold at a conference or on an infomercial for $99.95.

@Aaron Taylor Because of the slim margins, I figured I could buy Subject to the loan and sell on a lease option.

If agent fees are off ( I would think they would be 40k to 60k) deal gets real slim real fast.

Some flippers are doing close to that on sub 200k houses, so I can't imagine there would be much incentive for them to take on a 500k project with that slim of a profit margin.  

If it's $10K, you're still wasting your time because the likelihood of recovery is slim.

The chances of them paying out the rest of the lease are SLIM!