The "liberal arts" approach would be to tell you that sophisticated investing precludes buying either equity or cash flow - we create both, not buy them.A more mathematical answer would be to tell you that the 2 most applicable measurements of ROI are the cash on cash return (CCR) and the internal rate of return (IRR).  

I have a mathematics and physical education degrees.  

I have a mathematics and physical education degrees.  

From a mathematical standpoint, it sounds like they're trying to raise $1M for 1 year, and are offering 10% + a percentage of the profits, with a minimum of $25K.That means a minimum return of $125K (10% of $1M + $25K) for the $1M investment, or 12.5%.

Some tenants are just mathematically challenged.

@Jameson Triplett There's a lot of mathematical ways to look at this.

However that is only one side of the mathematical equation. 

For those of you who've had similar options, what kind of difference do you look for from mathematical perspective in order to decide whether to sell or rent?

Even though someone knows what they should do mathematically, doesn't mean that decision is supported emotionally.  

A lot of bad deals can be avoided by doing simple proven mathematics instead of guessing or listening to other people’s estimates .