Personally, I use our company's app as it's the fastest I have found, now that doesn't give me FSBOs and I think that Zillow is still the biggest platform used for FSBOs. 

A lot of new construction offer pretty good incentives like 10K towards closing costs or free upgrades. 

Systems which use prepaid cards or member cards/codes are better for the landlord (less incentive for theft), but are even more costly - unless your building is sufficiently large, the costs may not be justified.  

My biggest concern with refinancing is my credit 640 and the fact that I am now a one income household and had a career change that makes me significantly less money than what I was making when we purchased the duplex ($64,000 per year vs $27,000 although once the rental is factored in it’s around $70,000).

The biggest question is whether I'm legally allowed to pay the referral in Wisconsin to other licensed agents/brokers?

The biggest fear I assume most people have is that people will yell at you for being a vulture and trying to profit off of someone's death. 

The homes will typically appreciate, BUT as long as the builders are still putting up new houses in your area, there will be more of an incentive for buyers to go with the builder and buy new rather than buy "used" from an individual seller.

My math shows you with $450/month BEFORE those bills are paid.The biggest issue is going to be your Return on Equity (ROE).

It seems like the main incentives are depreciation and capital gains.

Your best bet in this situation is to keep heat on so that the property does not become damaged.You have already been told this, but your biggest mistake was letting the issue drag on so long.