This is somewhat subjective. 

Seller will consider a subject to agreement and wants only for the property to stop hurting their credit, because she is three months behind on payments.

Once you've worked up a repair estimate and gone through your numbers I would call them back for another face-to-face meeting to make your offer (I prefer back at the subject property...it's full of reminders of why they want to sell).

Hey BP,I will be acquiring houses using subject-to financing.

Find a distressed owner and offer to purchase the property Subject 2 their existing financing.  

Understand, you'd need to learn how to take a loan over subject to, which is a subject that you need to study up on.

It is an unbelievable fountain of information in a subject I am passionate about...real estate!

I think to harken back on the subject of this thread that this particular crowdfunding portal has seen a few of there deals not work out.. well that's just the risk of lending...

Would that cause any challenges for the person who is buying subject to?

It's a broad subject and everyone has heard a horror story, especially in the wake of the recent 'great recession'.