Hi Hillary,The easiest would be to go to your bank that originated your first mortgage (assuming you have a loan on your property).

My loans are all Fannie Mae.

Owner builder or building with a Contractor are questions I need answered plus any info I can get to improve my changes of getting a competitive loan. 

It depends on the type of loan, loan to value, fico, income, debt, and experience. 

So now we're looking at either just me on the loan (using both HELOC and mortgage, with him still paying 50% for my HELOC) OR both of us on the loan (with the down payment still on me).

And if there is a loan guarantee fee on top of the acquisition fee, that is another "upfront" fee that the syndicator can make just for buying a deal.  

Speaking from private/hard money terms, the loan would most likely be considered a delayed purchase if less than ~5 months depending on the lender, and no financing was used on the original purchase.

You could purchase a 4 plex with an FHA loan and live in one unit (house hack). 

You were a 5% owner if you owned (or are considered to have owned) more than 5% of your employer's outstanding stock, outstanding voting stock, or capital or profits interest.If you file a joint return, don’t count your spouse's personal services to determine whether you met the preceding requirements.

Also, it was for an owner occupied duplex, so I was able to leverage better financing terms with an owner occupied loan.