How to do a partnership safely

[Marcus House]

Hello everyone I have a question but first I have to give you a little bit of background. 

For the last 10 + years I've been buying single family rentals. This translate into me going to look at the property and put in earnest money into escrow with the title company and no money exchange in hands with seller until the title company obviously clears the title on the property and we go to closing.  I'm looking to scale but in a more passive way. 

How do I safely partner with someone on a large multimillion-dollar apartment acquisition as a passive investor?  What tips do you have for mean.  I already know about the due diligence process and how to look at the numbers and everything so I got that part covered.  I am talking about about tips that has to do with ensuring that I'm not potentially dealing with someone that could take off with my money.  Making sure thus is real.