At $40/foot its $110K ($130k @ 3239 Sq'), but not sure if it's accurate.

At best its a semi-educated guess, at worst its gambling. 

With that being said, I created a Excel model and like to get your input if the fields  captured are accurate and my formula assumptions are correct. 

If they accurately predicted the future, those that followed them would be over the top rich.

Don't know if that's still accurate but I'd be interested in hearing other people's experiences.

., then copy that into a workbook I use to track expenses and review how accurate my projection was.Scaling up, it sounds like QuickBooks is the way to go.

I would also think that the fixed cost method is probably more accurate but takes longer to compute.There are more variables to consider and get wrong. 

If it is not accurate you should know from the current rent rolls if revenue seems way off; and they should provide you with current leases, if you can prove they intentionally misrepresented the numbers they are probably open to legal liability especially if the real estate agent knew. 

If you really want a more accurate estimate on a payment, use something like mortgagecalculator .org.

I hear what you're saying about the cost to make them habitable but I don't think that will be considered a gamble when you're looking backwards a few years from now.