If you were able to build equity over time, it could be smart to sell, pay off your loan, and use the money for another venture (flip, investments, etc) if it is truly bleeding you out.

Selling your duplex could be a solid move if it helps eliminate your revolving debt and gives you a financial reset.

Then, if it is still negative cash flow, but the equity is there, then consider selling. 

Most decent lots are selling in the $50k to $60k range. 

If you are selling, definitely.

With one duplex you should be focused on selling 99.9% of the time and .1% on the duplex.

From there, I try to figure out why this house isn't selling, and if I'm still interested I'll make an offer at a price that works at my numbers.Other than that, yes I think it is a great idea to dig deeper into more creative methods of finding deals - wholesalers, direct mail, door knocking, networking, etc.

I have seen it too many times where an investor will buy an older property or even a new build, they net cashflow similar to you for a year ($100-$200 per month) and then a $5,000 repair or insurance/tax hike here hits them and it's a loss - they either get forced to sell or are majorly setback and unmotivated. 

My question is: when wholesaling, after finding a great deal, do you need real proof of funds to the get the property under contact or is there a way to get it under contract, find a buyer and complete a double closing/assign the right to sell without actually having the cash for the property? 

These companies selling products tend to drain agents dry at these conventions selling every do dad that is supposed to give them an edge over everybody else.