Is this your model?  

Most rental agreements require a termination to be reduced to writing.Then if a tenant were to stay beyond the agreed upon date, your action for possession would be much easier.I think it would probably be beneficial to get it in writing, if you don't have that already.Is there a particular reason that it would be a problem for you if she did stay until March 2 /3 - do you already have a new tenant lined up?

A revenue share model is fantastic.  

You can model it after others until you get some closings under your belt and decide how much or how little you want your hands in it.

To reach their success, these investors have had to implement different real estate investing models to see what works in this economy.

Copy other peoples models and work on it."

You may have a lot of unmotivated sellers contacting you with terms that will just not work with your model.

Is your plan to assign the contract or to take possession and resell? 

I can't imagine any other reasons someone would sell that low unless they are clueless, desperate or felt like giving up all worldly possessions and moving into the woods.

My analytical experience extends beyond real estate to stocks, bonds, and other investments.My spreadsheet modeling of potential real estate investments tends to be pretty detailed.