I've had the best conversations with smaller banks in terms of financing help. i.e. not Chase, etc. 

You may or may not know this but with an FHA loan, the property must be owner occupied for a year so deciding to house hack in LA is going to extend the beginning of your investing journey if you're okay with that.I am not too sure of the market in New Jersey, but I still feel that a property in LA is a better long term investment in terms of appreciation and desirability.

I'd recommend hiring a quality designer and general contractor who specialize in ADUs and know all the requirements.The best way to think about this is not in terms of the upfront cost, but in terms of the ROI and forced appreciation benefits you're getting in the long run.

@Dashiel C NeimarkDenver and Boulder are definitely tough markets, in terms of regulations and high prices.

I am definitely open to a 5% conventional for a duplex, I've been thinking in terms of FHA because the requirements are more clear when I Google around than a 5% conventional.

In terms of where to invest, it depends on your goals and location.

I would start calling now to interview them and see what the obligations will be in terms of monthly and annual fees/requirements/mls/association payments etc

How can I create a model without having all the details in terms of operating expenses and the state of the property that come with having a property manager review the books etc. up close?

From the comments I think I have an elementary knowledge in terms of overview of the industry but it would be probably be useful to buy some resources (ordered Joe Fairless's book) to go deeper in understanding deal analyses and raising funds.

It's a boutique so pretty unstructured in terms of brokerage requirement; there are a few agents who just do a couple transactions per year but Dominic, the managing broker is willing to be very hands on if you'd like him to be.