Hi @David Walker,
My 2 cents being a newer investor in Spokane with a house, a rental, and hopefully kids in the near future.
If you sold OR refinanced the duplex, you'd be able to qualify for another FHA loan in Spokane. That said, that also comes with PMI and higher closing costs, which you know stink.
In our house, we finished the walkout basement into a separate unit, which we rented for additional income. Our plan is to shift that to an Airbnb rental upon having kids. That way, we could have more control over determining the balance between our need to privacy/quiet with our desire for extra income.
Another thing to consider. Detached Accessory Dwelling Units (DADU's) are legal in Spokane, so you could potentially look for a primary residence that has the potential to someday have an apartment over the garage or in the basement.
If you are wanting to stay in real estate, I think this could be a good time to jump up a level on the pyramid. Capture your appreciation in Richland and look for a 3-4 unit in Spokane. Or, even partner with someone on, say, an 8-10 unit complex. There is a desire to play it safe, or get a larger house with kids coming soon, but I think that needs to weighed against the desire to continue building income producing assets, which will give you more freedom/flexibility down the road. There isn't a right answer, but it's certainly a discussion to have.
Lastly, my friend is an investor here and just refinanced his house in Richland. He's kind of kicking himself for not selling it and using the money to invest here. I don't know all his reasons, but PM me if you'd like me put you two in touch for a 20 min. call.
Best of luck, and keep us up to speed with your decision. Your journey and the lessons you learn will be valuable to others on the forum!