I recommend sitting down for an hour and learning how to develop a simple model in Excel yourself.When looking at properties you will often time have edge-cases where there are unusual sources of income and expense that might not fit in a calculator like this.

I've been following many Instagram real estate owners that provide tips and ideas.They make it appear so simple.

It's a simple and understandable number when speaking to anyone even those who aren't investors and you can call it "vanity", but others might feel it motivating in that seeing their successes simply like that and it might help encourage them to press forward even when things are difficult.

My first flip here in Chicago went smooth, simple cosmetic renovation, but then followed two average to below average flips...so beware no to get on a high horse like I did!

You can come to your own conclusion.BTW - simple question: Is it OK for a PM to share personal information about an investor with another investor?

This question is best answered with a financial approach and hopefully will be super simple. 

If it was easy, or simple then it wouldn't be lucrative to take on the WORK and RISK.

Too many people overlook the simple strategy of building wealth through equity. 

It’s a very simple one page document. 

I think you may want to start of the arrangement in a more simple fashion.Ask for a loan in which he will get a stated return 6% to 12%.If you are both successful happy with this arrangement, upgrade to a partnership.I think a partnership off the bat makes things complicated.You will also likely make more money in a loan agreement if the project does well.