We have prior experience flipping and leasing Single Family houses but new to apartment buildings.

Hi @Eric Gross,I think the best way for you to grow your business would be to get into leasing. 

Not to mention I'm also actively looking for deals (smaller apartment buildings, 5-24 units) where perhaps seller financing or a master lease option would be a possibility so I can get started without much of my own capital, but obviously these are difficult to find given my inexperience in finding off market deals.

During your due diligence you'll want to back up the financials with one year's utility bills, copies of the service contracts, and a lease-file audit (comparing the leases to the rent roll).  

A lease option would be a great solution to her problem since she is not in a hurry to sell bit is stressed, however its an older house and needs a lot of work hence the low ball offer.

Lease contracts?

I wrote her a vacant notice on May 2nd to inform her that I was going to sell the condo and would no longer renew the lease after July 31, 2018.   

. § 33-1368 allows for the immediate termination of a lease for the negligent discharge of a firearm on a property. 

You could do owner-financing instead, own the property rather than leasing it.

The trick to modeling retail is centered around evaluating the current leases.