I can roll in refi closing costs into the conventional loan as well.

I mean, I know advice on BP has been rolling downhill for a while, but this would take the prize!

Once I find and can afford that place, I can rent this one out and use it as passive income, or sell it and roll that money into the next project. 

Rent rolls, proof of deposit, or bank statements can verify the income.For expenses, utility bills make it real easy to determine electric, gas, water / sewer / garbage, if it's managed the property manager has their fee obviously but also probably tracks most of the other expenses.

(I asked her what she is hoping for out if this deal and this is what she said)She is looking for: $130,000 because she wants to pay off her current mortgage on the duplex (just under $100,000) and a personal loan that she took out in order to buy her new mobile home that she’s currently living in (about $25,000) as well as roll her portion of closing costs into that $130,000. 

If I can convince my GF, is it possible for her to roll over our portion of the profit as an "investment" into another property my business partner and I will buy with a 1031?

Or you could sell these properties and make, let's say, 30k on each of them and actually roll that into an investment that cash flows properly as a 20% downpayment.The key to success in this game is in scale, not in discounts.

So they don’t actually have funding for the whole development and need to utilize folks deposits to actually get things rolling?  

But simply glancing at the rent rolls, determining that the cashflow is poor and walking away is not value-add investing. 

All I have is a rent roll which only includes rent and deposit information basically.