Hi John, love your thinking here. Thank you for your service. I'd reach out to a local mortgage broker. They'll shop all the loan products that would work for your situation and give you your best numbers so when you approach architects and builders, you know your budget.
When you reach out to the architects and builders, see if you find one (or hopefully more than one) that seems willing to share their expertise in how to get the most value from your budget. Though have an idea of your target bedroom and bath numbers for your market. Ie: Is it better to have 3 units with 2 beds/1 bath or 2 units with 3/beds 2 baths, etc.
Ideally, you would have a good idea of where you would be building too. This is helpful for the design/bid process as there may be specific size, material or other requirements for a particular area that could strongly influence the project.
Once you have a sense of where the project will be built, a good idea of what you'd like to have in terms of # of doors and beds/baths, and the budget, reach out the architects and builders you would consider working with to request bids.
I think there's a lot of interest in new construction owner-occupied multi-family homes. Definitely a lot of need for it. Hope to hear more about your experience. Good luck!