I think in your shoes I'd have put in my original offer and wait for the counter.

If you rent parking and there was no payment that would fall under a storage type lien I think.

If I were in your shoes, I would go the route of raising her rent to $850 and taking a chance on her.  

@Chris Seveney, it is real estate that I plan investing in; particularly buy/hold commercial multifamily and storage. 

I have 9 units and 37 storage units.

I was once in your shoes.

Maintain or repair the existing structure or if you choose to rebuild they require you build on concrete piers and basically make the 1st floor (not sure of minimum elevation for 2nd floor) parking and storage.  

They were looking for direction on where to start in the real estate process, and I tried my best to give them the information on what I would do in their shoes if they didn't have the funds to pay realtor commissions, closing costs, repairs and everything associated with getting the house sold.

They handle all of the storage for you and allow you to email forms, do electronic signatures, etc.    

It's not exactly a "fair" assumption but you have to put yourself in the shoes of an owner who's being solicited on a platform where it takes about 3 minutes to create a fake profile and/or pretend to be someone else.