You could also take a look into corporate housing for Travelling Nurses/Doctors and others. 

To give you some info about myself...I graduated from college in May Debt free and am currently in the Medical Device Industry making 80k in year 1.

His wife's paycheck goes to cover their medical insurance and burden.I tentatively agreed to "hire" him to do this project--demo the existing old tile & backer board down to the studs, (bathtub is OK), create a new surround with ceramic tile & a glass band going around the 3 sides.

This is a loaded question that is near impossible to answer without extensive financial information on your client's age, responsibilities, income sources, other investments, insurance, medical needs, the list goes on and on.

According to Michigan law, Marijuana (medical or otherwise), is considered a "schedule 2" controlled substance. 

If they keep a clean house, they shouldn't have a problem.Most Landlords and Tenants don't understand mold and it's often exaggerated or used by Tenants to pressure Landlords into reducing rent, paying doctor bills, etc.

It's the trades equivalent of asking a doctor for a blank prescription pad.

If you have insurance, or property with equity in your name, a judgement against you could force you to sell and pay them cash for medical claims.

Doctors go to med school for 8 years and still get it wrong A LOT!

IF you're buying a home a $50,000 neighborhood don't think you'll get doctors, engineers as your tenants.