Welcome! Fellow army veteran here. I'm at 80% trying to get to 100% currently. Congratulations on your rating and I'm sorry for the injuries or ailments you are going through due to the disability. I'm just south in austin TX. I am no expert by any means but I thought I would drop my opinion here.
1) Should I focus on duplex since they're most likely less expensive in my area in category A or B properties, or aim for more units?
Honestly, this is up to you. I would suggest going as big as possible in the beginning. This way you can utilize the leverage if you plan to scale up in the future. The asset class will be dependant on how much capital you have availabile and how much renovations you plan to perform.
2) Is there an income gap between going after 2 units as opposed to 4?
Income will depend on your plan for the specific asset. # of units doesn't necessarily equate to how much income you could make. For instance if you buy a duplex and plan to significantly renovated it. It could provide more cash flow but your leverage would still be less due to the total value of that property compared to the 4plex
3) Is there an easy way to understand what price range I should stick to in my area, and should I focus on the best market or focus on the best price for properties?
Price range would again depend on you and how much capital is available to you and how much you are willing to put down. I would definitely focus on market growth oppose to finding a cheap property. A property could be cheap but be located in a low performing market. Therefore the growth potential is low as well. I would say Dallas is a solid place to start right now.
4) Once I've lived in the property for the obligatory year, is that typically long enough to refinance and use HELOC towards my next property?
I think a HELOC requires a certain LTV before you can pull any equity and 1 year most likely won't be long enough for any real equity to build.
I would say. Live-in-flip a four plex- live in one unit while you rent the others and benefit from the other 3 units paying a large chunk if not all of the mortgage. And renovate yours while you live there. Depending on your living requirements and your specific situation of course. Then continue moving from one unit to the others until you renovate them all. Depending on market growth, you could utilize the HELOC to pay for the renovations. Once they are all renovated. You could leverage the value of the entire four plex to put towards a larger asset or try to 1031 exchange it.
again, i am no expert but I would consider myself a fairly savvy investor. I would love to connect and see if there are any ways i could help you further! Good luck!