Currently I’m using Zillow’s background check, and I’m screening all my  tenants  before they sign a lease.

Multiply that by 28% (technically you'd now be in a 25% tax bracket if single but bear with me) and your tax liability is $25,200.

Our current rent is $2600 I want to offer to pay $3000 for as long as she wants 1-15 years and then pay $600k My main question is whether that type of structure of offer makes sense legally or technically or practically. 

If, for example, I could get hard money to purchase/repair and pay off in a year, I'm confident I could do so without loss, but only if the payments could accrue in the background, collecting interest, without being paid until the house sells.

If you had a written lease in place double check what it says about your security deposit- even if you didn't technically have one.

Pull standard crisis and background report.2 Take care of maintenance on routine basis3 Check with prior landlordHave printed acceptance guidelines to avoid fair housing complaintsBob CollettRemax Trinity

@Jennifer Solesky for background, I am a managing broker.

Here's some background that might be helpful: My mom died last year unexpectedly.

What I would suggest alternatively is putting a clause in the lease that anyone above the age of 18 that's going to be living in the unit for more than 7 days has to be approved by the landlord and pass credit/background/income check etc. 

In conducting a background check, I learn the applicant's current neighbors hate him, he's on a first name basis with the local police or he has a variety of other social/criminal issues chasing him.4.