I know there are other methods to obtaining a deal and wholesaling It on the back end like double closing or JV but all situations are different of course and not all wholesalers prefer to JV and split profits.

Sometimes investors think a duplex is more valuable based on the income it generates. 

How do i know what is the most i can offer to win the contract, so that the buyer and I can turn a good profit?   

I'm able to put down exactly 20% in down payment for the new house purchase.Is it a better overall strategy to keep/rent out the condo which is expected to net me a yearly profit of about 11k after taxes and HOA common charges and simply take out a 520k a mortgage loan for the new house ? 

Work out a deal where you earn a percentage of profits without risking any capital.

For example, in Houston right after Hurricane Harvey.The disadvantage for you is that you will be giving up some of your profit from appreciation.

and one guy said he wanted to buy and actually asker to finance 15k. smh. seller wasn't gonna wait for 9k. one of the buyers was a real estate agent. and he was just coming to look for his out of state buyers cuz he said it was something they may be interested in. but after coming. he said something about a non profit had bought it prior to my seller owning it. and something about the next buyer not being about to sell it for too much because of that. which i have never heard of before. have u

Then you can either sell it for a profit, or refi and keep it as a rental.

I did flips to help generate cash to buy my multifamily buy/holds when I was starting. 

Is there enough profit in this deal for it to make sense if you give up half the equity?