Think about it as a reward to the tenant for staying long term. :-)

Since this is my first time, how do I screen the investors that they understand the risks and rewards?

As I'm sure you're aware the greater the risk the greater the reward.

You can maybe maintain the land for the house you want to keep as half the parcel but divide the other half into half or thirds.You can also just sell off the parcels less reward and control since your mom will have to look at whatever they chose to build but less risk. 

All transactions have risk-reward relationships and values have means for justification beyond gut feelings.

However, the reward has been very limited calls at the midnight hour to fix things.  

Alternatively, you can also invest with others who are experts at all this, reap the rewards and really simplify your life.  

Risk vs reward is not there.

It's simple risk/reward economies of scale that the big guys will be willing to gamble their 100K at lower rates/points. 

Always balance your risk and reward.