Once you have determined that, then ask for a comparable market analysis of properties active or sold in last 6 months.

This may sound harsh, but just make sure you have an operating agreement among the two of you.

Then compare her spreadsheet vs. 

So I got out of class last night and my professor was telling me that, in order to do an income(investment) property, you will be charged with a higher interest rate compared to a property that you would finance for yourself.

(2) Does it save money when compared to buying a retail house of the same?

The risk to the seller of using lease-options (or any other executory contract) is now significant, and investors should therefore use any such device with extreme caution.Note: lease options are not illegal, just harsh in penalties. 

IMO $800 is money well spent compared to what you can save.  

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That compares very well with the 16 - 25K of tax plus depreciation recapture on a profit of 80K .The real question is can you find good replacements that fit your parameters within the time constraints.

The house sales and rentals are down compared to previous months.