Primary?  

However there are lenders that can go up to 90% CLTV  (HELOC) on a primary residence. 

Lenders will happily use future rental income but not when it's considered your primary. 

I’m trying to get a heloc or cash out refi on a primary residence duplex.l under FHA.I have great credit but modest incomeWife has bad credit with better income therefore I don’t believe we will qualify for heloc.Our plan was to get heloc to use as a down payment on another house hack or general investment property.So far our mortgage company said they could do the cash out refi which would raise our mortgage from $800 to $1200 (current rate is 3.62) and the rate would go to 6.6To pull out hopefully 30-35k maxMy concern is if I do the cash out.

If you truly just want your primary paid off you can just do a cash out refi on your investment, still in your own name, and pay off your primary.

So it can be much better to keep the existing policy, with you as the primary insured entity, and add the wrap buyer as additionally insured.

California is one of the states that will hound you for the proof your 1031 is still valid, only a California expert could say if converting it to your primary would trigger that tax.

I see other people have their primary residence as an LLC however. 

I live in CA and own my primary residence. 

You could buy a home for a primary residence, rehab it, and then sell it after living in it for 2 years as your primary residence.