A purchase agreement is one of the first tasks to be uploaded int WF equator system.

Considering just the property and the financial side of the equation it comes down to the numbers and the area.

@John Lowe   it will simply be NPV equation for a note investorBack in my days when I bought timber land...

I think it's just as simple as your equation.  

A payment of $1K per month on a $350K would equate to a 0.19% interest rate amortized over 30 years.

What it covers doesn't seem to equate to the 10% that you've allotted so you're paying more and getting less. 

And rent loss and capital costs are part of the 50% as well...Try watching this very unprofessional video I put together that will explain it better:http://www.biggerpockets.com/forums/311/topics/72246-the-50-rule-video-tutorialMortgage payment (principal and interest @4.75%) = $652That's the other important part of the equation for doing the rough analysis...If your gross rents are $1200/month, the 50% rule says that, long-term, your NOI will be somewhere in the vicinity of $600 (50% of gross rents).

Disclosure:  I was a licensed agent for 3 years....I understand both sides of the equation here.

You have half the equation, the contract.

I am assuming that is your 0.70 factor in the income equation.