It is a mathematical calculation that can be adjusted by changing the inputs.I would look at this point for a strong market fundamentally. 

He's finding more properties than I can get qualified to purchase.If you're looking for commercial (5+ units) @Nathan Holsather is a good bet as well.If you're looking for someone who does value-add residential, @Jordan Moorhead is both a rehabber and an agent.

Hypothetical deets (all numbers are rounded):30-yr Mortgage: $280k @ 4.8% Dual net monthly income: $9kTotal monthly expenses: $5k (includes mortgage payment)(Cash Flow: $4k)Plan is to use a Line of Credit (18% APR) and pump $15k into the mortgage every 6 months (conservatively paid off in month 4).Using this approach (per the amortization schedule calculator I have) I will pay off the mortgage in less than 7 years.I will pay around $11k in Credit Line interest (approx. $700 each 6-month iteration), but will reduce my mortgage interest by over $200k!

For another, is the investment sponsor forecasting that the exit cap rate (the number they are using to calculate the exit value) is the same, higher, or lower than cap rates today? 

It does not meet the 50% rule, but the calculator shows that it still has a positive cash flow and ROI.

Would a HML be my best bet on this property .......... as i may have a better chance for being approved to do most of the repairs , as well as Having the best chance of getting a loan for the property?

The conventional may be my best bet, but I do have my house that I can work with.

SO, is there a formula to calculate current equity value or resale value vs income, I should look at. 

Your best bet is to have your agent contact the listing broker's employing broker and let them know the situation and request to be present when your offer is presented. 

I have never seen a expense calculation when evaluating a property for voluntary below market rents.