You wont be able to scale to 10-15 properties by using all you cash flow to pay each one off....and you wont be able to live off of one paid off property.You are going to have to leverage and then once you scale to your desired level, then start paying them off

there is just a ton of debt you have to take on and as we age we get debt adverse.. now in new construction we take on debt of course but we retire it.and yes its a job.. but when its in the right market cycles boy is it a good one  Can make more on one new build in 9 months than a rental house in 20 years.. so its just scale. and what you want to do .. 

Some think it's less risky to have moor doors because you aren't hit as hard by vacancy, can take advantage of economies of scale, etc.

Or find other investments to build on a smaller scale for now.Some jobs are worth keeping in the short run for how much they can pay you now, you save every thing you can and invest it. 

can you actually scale this into a business...

I can't scale the single property! 

In terms of reaching your goals, you need to scale up.

I'm starting to think we should scale down and include duplexes and sfr in our immediate plan.

I would think that in a 30-unit there would be a greater economy of scale and would cost less per unit to submeter, but I'm not 100% sure.

In any case,   one argument FOR holding onto smaller apartment properties in seattle is that townhouse redevelopment,  which requires the same zoning as small multifamily causes a lot of SFR and smaller apartments to be lost to redevelopment,  so this class of neighborhood scale and typically comparatively affordable housing is going to get harder to come by,   and presumably in higher demand as a result.