While the guarantee of income sounds great, it's only a percentage of the rent, typically up to 70% and the tenant has to pay the remainder.

Next, what percentage of the real estate will you own? 

I question what percentage of those who invest in RE unleveraged actually understand the numbers and how extensive their underwriting effort.  

Riskier assets are lower percentages.

Deduct NEW property taxes after you buyDeduct home insurance costsDeduct maintenance percentage, typically 10%Deduct vacancy+tenant nonperformance percentage(we recommend 5% for Class A, 10% Class B, 20% Class C, good luck with Class D)Deduct whatever dollar/percentage of cashflow you wantNow, what you have left over is the amount for debt service.Enter it into a mortgage calculator, with current interest rate for an investment property, to determine your maximum mortgage amount.Divide the mortgage amount by either 75% or 80%, depending on the required down payment percentage - this is your tentative price to offer.If the property needs repairs, you'll want to deduct 110%-120% of the estimated repairs from this amount.Be sure to also research the ARV and make sure it's 10-20% higher than your tentative purchase price.As long as the ARV checks out, this is the purchase price to offer.It is probably significantly below the asking price.

You can negotiate a flat fee, or percentage of their profit of any deal. 

It ranges in percentage but nothing has felt different.

It is very algorithmic-ly dictated based on and numbers and percentages. 

I wondering about cashing in a small percentage of my stock portfolio to fund my next RE deal.  

If it were to read LP member owns XYZ% and will receive a certain percentage of proceeds based on property performance, that's a different story.