The lease that the tenants were on was poorly written and has no protection.

You'll also want to check with City zoning to see if there are any other things that must be done to the property before leasing to a commercial tenant (think ADA, etc.). 

Assuming she is M2M or at the end of her lease I would give her notice you will not renew her lease at the end of October. 

My agent has told me they do not want to list my property for sale yet due to the fact that my tenants have over a year left on their lease.

I have some experience, having knocked down a drive through location and replaced it with a national food service company in a nice town and then also purchasing a historic bank building and leasing it out as office space. 

At the same time we cleaned down everything with bleach and other cleaners like TSP.

I did a "lease-option" with him where I essentially took over ownership and responsibility for the property as if I owned it.

Just rent it furnished and gear your lease, and rents towards a shorter stay.

Review their lease agreement and addendums.

Commercial properties prefer long-term leases of multiple years.