Ive asked them to provide Renter's Insurance.

I interpretttev @Alan Asriants statement different than you but agree it is not clear   He could be indicating pools, basements, sunrooms do not provide a means for an extra tenant.  

The seller was willing to take a secondary position on other property assets and provide a 3yr 4% interest on his loan.

Most MTRs in my area include utilities, but my California property has very high utility costs (PG&E - could easily be $1000/month with regular AC/heat use).

This way, you can easily revisit details and pick up right where you left off.Avoid cutting corners to save money, as it often costs more in the end.

You can easily look them up on https://nmlsconsumeraccess.org/If they are a commercial lender, you may want to check for google reviews

He could provide you with some good insight in and around the area!

You are considering putting a tiny home on your existing property as an ADU or using that money to save up and buy the next investment property and wondering which would be the wiser choice.I think ADUs can help provide additional, much needed, housing.

Now the post test reveals I have pvc sewer line leaks under the concrete foundation. plumber has found multiple breaks in the line which need to be repaired and has provided an estimate for tunneling under the house and replacing entire 45ft main line!

My conclusion is that take the provided ROI calculations from REI as purely estimates.