Any advice on most efficient and costly ways to obtain marketing lists in S.

What market are you in?

If there is any way you can avoid marketing to section 8 you will be far better off especially in regards to the quality of tenant you will get. 

@Dave Rav - I agree with the others that there is no really good way to estimate insurance costs, but I've found some consistency within a particular market/zip code if the rebuild costs and deductibles are the same.

I'm thinking about ramping up my marketing and having agents send me deals with their criteria.

I have searched online and found no company or market for this type of transaction.

That is a very general question and each area has its own market conditions so what works well in one area may not in another.

Sat on market for 4 months before they dropped to $125k.

Historically real estate and markets are nearly identical over a long period of time. 

So as a listing agent/broker I will need to be more optimized for this marketing and processing of inquiries.