Hows is that going.. currently my tenants pay all the bills but I am wanting to get a HELOC on the duplex.

You're already at 90% LTV so a HELOC will likely not be viable.

I also can go higher prices by tapping into a heloc for part of downpayment. 

Renovations completed using our HELOC.

If my primary residence has $500k HELOC, could I use it to purchase a 2nd primary residence and rent out the first one?

Quote from @Josh Fugle: Dti ratio for helocs and being too “new” are my problems.

It was originally purchased for around $150K in 2020, with a $50K HELOC added in 2022.

Make sure you know the value the ADU will add to the property before building the ADU. 2) the financing on an ADU is typically far worse than for initial investment property acquisition or is often not leveraged by the ADU (HELOC, cash out refi, etc).

Own one home currently 1,770sqft 3bed2bath. 15yr fixed 2.625% -- Mortgage +  Escrow $1650/mo, worth $365k, owe $135kTrying to buy a $400k home to move the family into, but keep our current home as a rental property.Considering refi, heloc, or home equity loan to access equity for $80k down payment.Would rent my current house for about $2,100-$2,400/moCan someone with some knowledge/experience tell me what's the ideal way to access my equity to make the most investment sense?

I’m trying to get my first HELOC done so I can continue to acquire more doors.