But, that sounds a high-risk low-reward behaviour.

I’m not an expert of the area by any means however I looked at several properties in the area and the two big takeaways for me we’re 1. the rents-to-purchase ratio are fairly low and 2. you’ll likely be dealing with large, older families.

Lenders are saying our income is too low.

Lenders are saying our income is too low.

You can get a loan for slightly cheaper depending on your credit score and LTV that you are looking for Ive seen as low as the high 5's to mid 6's on the interest rate 

You can try to justify a low offer all you want, but chances are somebody else will come by and pay what they are asking. 

I am considering making offers at what could be considered low ball prices (30-50K below listed price).

I can absorb the worst case scenario for one ARM since everything else I hold is on low fixed rates and cash flows well, but I'd be wary of collecting a bunch of ARMs like this if they all have the potential to go negative cash flow.

If you live in a low cost area in the United States this can become easier to accomplish versus an expensive part of the US like CA or NYC where you're going to need a lot of cash flow to meet your goals.    

Make sure there is no or low interest.