Trying to compete against a builder to sell your existing build is extremely difficult.If there is new construction similar to yours around what you're selling you'll be at a disadvantage unless the market is scorching hot again and the builders have waitlists like they did in the recent past.Let me know if you have any other questions or need help in those areas.

I think a perfect world would be convincing the owner to sell me the properties by assuming the existing mortgage and maybe giving him a little something extra.

I am starting a park that will end up with roughly 20-25 lots on plot of land that's roughly 20 acres (including an existing 4/2 house).

IT Business:With $250k in cash savings and significant untapped equity in your rentals, you’re in a strong position to leverage your existing real estate knowledge to grow your portfolio further.The real estate market, particularly with your ability to do your own rehabs, might provide you with more immediate and scalable opportunities for wealth building, especially if you can find properties that need work and force appreciation through value-add strategies.Balancing Both:You don’t necessarily have to give up the IT business entirely.

Those tax breaks existing in the first place are examples of politicians intervening to artificially change market dynamics, by stimulating investors to buy those properties more aggressively than they would in a free market. 

This implies that cash flow growth historically is non existent in inflation adjusted terms. so the $122/unit cash flow is unlikely to increase in inflation adjusted value   It appears that numerous expenses are missing, the property historically has depreciated in inflation adjusted dollars, and even with the expenses you provided, it cash flows $122/unit    To me this does not justify the effort of owning residential units.  

The two primary banks I worked with no longer exist  and all of my original banking relationships have moved onto different banks/lending institutions.

And you can avoid the large transactional costs of having to sell your existing properties.Since you can cashout refi up to ~80% LTV, you're not going to get that much more capital to upscale by selling and doing a 1031. 

I painted it, redid the floors, put on new doors and hardware, fixed all the existing issues (leaks in roof, toilets not working, sinks leaking, water damage on exterior and upgraded the panel to a 220V) What was the outcome?

I plan to remove two existing houses and build ~3 new ones.If anyone here had similar projects in Bellevue, I’d love to connect and learn from you.