I’m starting a new build of a duplex that after completion can net me 200k profit.

You'll need a much lower priced property with some value add or larger equity spread, and also have the funds to make the payments in case it doesn't play out so smoothly, or there's delays getting renters/lease-option buyers, etc... 

Should I sell for a small profit and use the cash to make down payments on multiple properties?

I have yet to hear any input on thoughts for what works out better, what makes more profit, what makes loans easier to obtain when it comes to flipping a house in Philadelphia.

Duplexes or larger. 

And I don't see supply catching up anytime soon -- sound off if you don't agree, maybe you see something I don't.I read in some other threads here that the new stuff being built is the newer/nicer and larger scale MF units, and obviously that is going to rent at higher rates, being newer/nicer and all. 

:@Peter Prawel someone made a post here once talking about how his hard money lender kept backing out of his deals only to find out later tjat the lender bought three of them himself and kept it secret while still getting him to bird-dog more dealsmost real HML I know the last thing they want to do is rehab houses LOL.. they are busy enough just keeping their own loans on track. can it happen sure it can.. but is it the norm with larger known HML  no way.. 

That is a strategy that we have done but particularly early on when we didn't know how much better it was to stay in the deals (better for the seller and also more profitable). 

If its not cash flowing or appreciating fast enough, and you can profit out of it now and have other better deals lined out, SELL SELL SELL!! 

Larger families, same idea.