the solutions suggested that hold the open sash in place, pinching the AC unit in its place will not work against a thief with the leg strength of a teenager.

I don't have a good suggestion but am interested in this topic as well.

Any suggestion and or advice on how I should approach this situation would be greatly appreciated.

Any suggestions or recommendations?

@Timothy Lee thanks for the suggestion.

I did contact her to see if she would be interested in private financing for a higher amount (was thinking I could do as has been suggested here, then logged i today and saw that almost exactly the same thing was posted as a possible solution, so im waiting for her reply.

Your suggestion to stress test makes perfect sense. 

@Dennis Villamor -My suggestion would be to hone in on 2-3 neighborhoods in the region that interest you and start checking out what is available.

I live in Bay Area and nothing around here comes even close to suggested buying formulas. 2% 50% etc.

Love @Mike Dittman 's suggestion.