She wants to sell the house to me for only what she owes on the house, so it could alleviate some pressure from her financially. 

How does one alleviate this concern of purchasing a vacant property?

Due diligence does help alleviate a lot of issues that come up with tenants.

One other direction you could consider is getting a slightly larger property, say 2-4 unit that would alleviate your low loan amount issues while opening up increased cash flow opportunities.

When accepting payments, you should look to receive them online however, if your tenant insists that they mail it, you should write it in our lease that if payment are mailed the tenants need to ensure they choose a traceable mailing option - which will alleviate you of the burden of having to listen to tenants tell you they mailed payment when they didn't. 

Also--to your second point, the reason I pay a property management company is so I can alleviate my need to have to manage my own properties. 

I get a lot of nice NW San Antonio properties with slight foundation issues and having a good slab contact could help alleviate a lot of the unknown for my clients. 

I.E. according to HUD, the animal must “work”, provide assistance, perform tasks or services for the benefit of the person with the disability or provide emotional support that alleviates one or more of the identified symptoms or effects of a person’s existing disability.Individual animals which are known to be aggressive are restricted, regardless of breed.

He is super good with customers and is able to alleviate any heightened emotions and can recommend many places to see/do.

"Traditional" self storage facilities help alleviate those pieces of the puzzle.