He also tends to do all work himself, so I feel like the hassle biases his thoughts.

Maybe I'm biased, but I'm going to have to disagree with @Cody Alexander, @Luka Milicevic, and @Claire Trammell. 

So, I'd only do it as a personal loan and you'd be on the hook for principal and interest regardless of the outcome.To even consider some sort of profit split it would need to be very biased toward returning my capital.  

The scores themselves are not a valid prediction of paying rent and there's strong racial and gender bias baked into the score. 

An architect that understands investing (even better if they invest themselves) is a huge asset to a team and is under rated IMO (i know, obviously a little bias haha).

FYI, I'm biased because we have two little ones, but that means I'm also living proof that it matters.

As an agent and investor, I'm biased to the Destin area personally; however, I have plenty of investments in other locations. 

I am bias in that, I preach for people to buy homes and build wealth but I also believe in business and being creative! 

I may be biased, but in my opinion this area is experiencing tremendous growth with no signs of slowing down making it a great location for long term investments. 

Bigger Pockets is simply "bias affirming".