When it is paid down enough you buy your next property.

Of course the owner didn't read the paperwork they signed so they go under contract thinking only of the 1st they are making payments on.Total debacle once the facts are discovered.Before going one step further I would be absolutely sure there is "no 2nd" because it is just as likely that there is a 2nd... it just isn't getting paid monthly.

They are likely to send their off-market deals (pocket listings) to investors they've worked with in the past and know will close so that they can get paid.

As well, and assuming necessary, once done, you can advertise this upgrade and the positive resulting heating and cooling bills in future marketing when the need arises.For straight rentals (not a property sold via Lease Option, CFD, or other Owner Financing), I never pass large expenses on to my tenants (pretty much anything over $300, unless their fault), but assuming this is a defect or need that I did not see in my pre-purchase home inspection report, I will just deal with it out of my own pocket and earn a bit of positive "good landlord capital" in the process.Good luck with it!

She wanted to move in September 15th, so she also paid me for half of September and signed a one year lease.

My question is how do I protect myself to get paid the $550 to $1,000 for finding the property when the person purchases the property?

They have always paid on time, but recently a tenant who just move in just over a month ago wrote to me that she would like to sublease the unit and was looking for my approval.  

Yes, but only if they paid for it.

I am pretty sure there are implications on my end they have a lot of furniture here have paid for moving expenses etc.She has also paid for utilities as well. 

ummm I do this all the time (in reverse) should be a deed transfer and it's super easy.is the house paid for an owned by you?