I was using the BRRRR calculator and wondering: what are the biggest contributing factors to the Cash on Cash ROI calculation?

Seller can contribute up to 6% CC (based of purchase price, not as-is value).

With the $20K contribution and the same 20% compounded return, over 10 years, you'll have over $700,000.Btw, if you invest that $700K earning 12% cash-on-cash return in a long-term rental property, you're now earning $85K per year, completely passively. 

Much of that will normally come from a really good buy and also a significant capital contribution from you, a partner, combination. 

You could also try partnering with someone that does have proof of income and split the equity or pay them a fee for their contribution to obtaining financing. 

Not looking for a handout - happy to contribute back for your time.Thanks!!

Even for Milwaukee standards in any decent neighborhood it is not possible for a duplex house hack to actually cash flow - you are basically on a 50% vacancy.The way you should look at the deal is as if you would also pay rent: now you should be cash flow positive.Most of my younger clients will end up buying in the $200-250k range and end up contributing a couple hundred dollars a month to make PITI, depending on loan program and down payment. 

Do they have someone willing to contribute the difference so the deal closes, and they can continue raising until that lender is repaid?

In this case, several individuals participate in one first position loan and share ownership based pro-rata on the amount they contribute.Last, simplest, and completely illegal if you do it incorrectly, is to form an LLC and have your investors make capital contributions.

Thank you to everyone thats contributed, since I can't post the agreement as an attachment, I'll be going to a contract lawyer.