About 3 months ago I told them they were in a lease violation since someone was smoking medical marijuana. 

It's a math exercise. 

As the Optionor, my concessions start at 3% if exercised within first 12 months and decline if exercised later.  

He gives them 3 years to exercise the option to buy, during which time they can work on improving their credit, saving money, and whatever is needed to help them secure traditional financing.

I would not say this was a failure...rather an exercise in good business practices.

There's a rope pushing exercise (from my experience anyway)...

My idea is to enter into a Lease Option contract with the seller and take over their loan payments without receiving any equitable interest in the property until I exercise my option to buy, so as not to trigger the 'due on sale' clause in the mortgage. 

I can also give you a referral on a property management company. http://www.forbes.com/sites/erincarlyle/2016/01/27...http://www.forbes.com/sites/ingowinzer/2016/07/29/...http://www.crainsdetroit.com/article/20150607/NEWS/306079987/planners-seek-to-make-grand-rapids-medical-mile-a-healthy-place-tohttp://fox17online.com/2015/03/17/grand-rapids-rental-vacancy-rates-lowest-in-country/http://mibiz.com/item/22318-grand-rapids-said-to-have-lowest-rental-vacancy-in-the-countryhttp://www.michigan.org/blog/guest-blogger/three-reasons-why-grand-rapids-is-beer-city-usa/

While I am recovering still from a medical problem I have read a book about buying small apartment buildings and the ability to add value by Lance Edwards and it was real good.  

I am 59 years old now and I found BP about a year ago and I have still not decided what to do while I recover from a medical problem.