You have let him stay even though he has lease violations.  

They talk about this a lot on the podcasts - I think pick some areas you are comfortable driving to and start exploring those.  

So I feel very comfortable writing up contracts.

I would stay away from them.

Stay on the look out for the BP Events and Happenings page, I always post it here on Bigger Pockets and email blast everyone.

But despite all these mistakes I've owned the property for 10 years, it stays rented, and I have about 40% equity.  

But in general a 24' clear masonry building in good shape for its age and ability to add value through reverting to multi-tenant would be attractive to me and so long as your comfortable with the tenants credit, your return and ability to release it in 6 years if needed then go for it. 

If you are not comfortable with the answers, I think that you know the answer to your question.

I'm not sure that I would sign up for something like this without being confident that I'd be comfortable with this person as a business partner.

@Jennifer Preddy Egbert that is an interesting way to spin the offer... sometimes the idea of 'free something' can give it more weight than it would otherwise carry. just need to decide if worth having a tenant in there, would want an airtight lease in case she changes her mind and wants to stay longer...