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? 

(they're actually starting to slightly pickup).

To answer your question, I will use your description as it most closely relates to my definition of what an actual turnkey real estate transaction should be. 

There are the obvious pros/cons of a duplex but then there are the non-obvious ones that come with being in Detroit.I actually have a fantastic article about this I can share but I'm unable to link to it in this post.

If it is a private money/ commercial style  lender, it is a relatively simple process.

After talking to support (who were actually quite responsive and helpful), they told me I had to publish the ad with only one photo first and then re-post the ad with additional photos later to force the first photo to be first.

The 90% they are paying you back is probably 1/3 of what they're actually making by you committing to a deal.

If you had also spend money on renovations and improvements while occupying those should have gone into service then as well. 

Hey @Sundone Boutvyseth,Mountain America actually has a private loan program for Utah investment properties that is only 10% down.  

While raising money is an important skill, what makes or breaks the investment will be operations.