The leases I had includes the option, no time limit, and no specific purchase price.So somewhere along the line, the tenant notifies you he will exercise his option to buy.As to why, plenty of reasons.

Just notify them, per the terms of the lease of course (ours is 30 days notice on month-to-month contracts), that you are exercising your option to terminate the lease. 

At the end of the term they exercise their option agreement, execute an agreement of purchase, get approved for a mortgage and take title of the property.Make sure you work with an experienced mortgage broker and lawyer to make sure you do things right for your area. 

It also has been quite an exercise in sweat equity, and learning to see everything from the guest point of view as opposed to our personal biases.Hang in there!

Define default and what happens if you go into default (ie. exercise their rights per the deed of trust which spells out how they take control or sell the property)This isn't everything but it's a start.

The way you have proposed would be the most costly way to do this exercise. 

In our small town the fire chief will do it.Approach yours & suggest it as a training exercise for their guys.

I feel that is usually an exercise in frustration. 

The seller/landlord retains full value on the lease payments though if the option agreement is never exercised. 

(iv) If Buyer is unable to obtain Loan Approval after the exercise of diligent effort, then at any time prior to expiration of the Loan Approval Period, Buyer may provide written notice to Seller stating that Buyer has been unable to obtain Loan Approval and has elected to either:(1) waive Loan Approval, in which event this Contract will continue as if Loan Approval had been obtained; or (2) terminate this Contract.