Both of our properties have about 100k in equity in them so we were thinking about using getting a HELOC on the duplex rental property and use that money for the down payment on the next property.

It seems not the best way to spend money.

I have a trailer house for sale, but I have need the money out if it faster.

Yes, the more deals you do, that are profitable, the more money you make. 

This is our first investment together so we're exploring financing options.Wondering if anyone has trusted contacts in private lending/hard money who are able to fund ~$400k in acquisition cost and ~$250-300k in repairs?

What have you found is worth the money and what isn’t?

So many "investors" bury themselves in complex, expensive situations to protect themselves from some unknown threat to their non-existent business.Figure out if you have any shooting skills (or even enjoy the game) before spending money on $600 Nikes or an indoor basketball court. 

Be prepared to spend some money though.

And your money is Trapped inside your house. 

If they want your money, @Pavan K., why aren’t they offering you a stake in the partnership?