The property currently has a tenant who is paying below market rent at $850 per month.

Is it just this market that is bringing fear or has it always been this way?

WI is a big market. 

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.

If not, and if these are homes that are in a market where dispositions are not too daunting you are likely best served selling these homes and re-investing in properties that can lead to additional equity.