You make a good purchase, increase the NOI, pay down some debt, double your equity and move on (via a 1031 if you're smart).

Had to chase the definition to understand this one:http://www.investopedia.com/terms/c/contractfordifferences.as:- DEFINITION of 'Contract For Differences - CFD'An arrangement made in a futures contract whereby differences in settlement are made through cash payments, rather than the delivery of physical goods or securities.

I was wondering if there is a way to use the potential income from one side of the duplex towards debt to income ratio?

As a wholesaler you should know what to do and how fast you need to do it.Here are some suggestions:Write an offer for what she wants.Take title subject to the mortgage, keep the property, pay the mortgage and profit from the rent and appreciation -- orControl the property with a "skinny contract of sale" with a delayed settlement date, have a public auction.If you control the property for $65,000 and sell it at $80,000 you are doing well (need a partner).I'd say stop asking question and go close that deal.May I ask you some questions?

I can't ask the bank for another loan, not based on my "Debt-to-income" ratio, or at least I don't think I can.

Apart from finding high cap rates and being okay with being in debt up to your eyeballs, are there any other methods of growing quickly?

Where people get in trouble is when they look at it as a pay day and put the money in the bank to pay for bad debt, trips, cars, bills etc...Use your cash flow to pay for these things, after you have some reserves!  

That won't make you feel like your drowning in debt!

Do I have any debt ...nope, nada, zilch...so the prospect of paying for a house outright was a simple matter of “yeah I don’t want any debt servicing” but I didn’t take in consideration the cost of self financing.

And keep saving and pay off any debt.