I have used avail.co in the past with great success but it appears this software and others no longer market on zillow which I know to provide a lot of leads in the past. 

No guarantee this will continue but I see elected officials making policy mistakes that will lead to less development and that makes me believe constrained supply will continue to drive above average appreciation.John

As I start down one path, I have more questions which leads me down other paths with even more questions. 

For smaller deals like owner finance options, it's important to build a strong relationship with the seller, as this often leads to more flexible terms.

I've learned that the on-market opportunities just don't have enough margin and are too risky for flips.If you have any off-market leads or know where I should be looking, please share them with me!

From what I've seen and read, most of the reason operators get in trouble is that there is some type of "event" that has occurred (usually their loan has matured or they've defaulted on their existing loan) and they need to refinance their loan and the lenders require a new appraisal to be done, which usually leads to a lower appraised value, and a lower loan amount, which "forces" the owner to pay down their debt.

If the land is in a suitable location, this could open up opportunities for developing 2 homes or even selling off one of the lots, which could lead to a good profit.

Whichever method of lead generation you decide on, aim to establish and maintain a relationship with prospective sellers. 

An undersized septic system may lead to compliance issues, maintenance problems, and costly upgrades.

(New York or CA and those following their lead.)