Definitely a good one. 

In the community's opinion, is this worth pursuing from a legal perspective or do we take the hit and move on with the deal? 

If you sign a buyers agreement on the purchasing side or a listing agreement on the selling side, it is a legally binding document and the agent has a fiduciary responsibility to work in your best interests just like you have a legal responsibility to make sure the agent gets paid at the closing table. 

This is the textbook definition of penny wise and pound foolish.

and are there any legal restraints that I should be aware of before pursuing this niche? 

The lady whose sister died, can call the cops and report him if she has permission from the other legal occupant and documentation saying her sister's stuff is for her.

I definitely would love to connect!

Make sure you review those before buying so you aren't stuck without a, legally viable, business strategy. 

A broker representing the seller has a fiduciary duty to warn the seller as to the risk involved and advise the seller to seek independent legal counsel. 

An eviction by an attorney is probably not as expensive as you have heard when you consider only legal and attorney fees.