Do rehab on house and bring it up to level of rapidly rising neighborhood.

I also wouldn't do a lease longer than 1 year because your rental comps in the area might rapidly increase as the area develops. 

Your title calls yourself a "developer", so if you have activities you engage in that create earned income instead of just passive earnings, then that might qualify as self-employment.A Solo 401(k) can hold both tax-deferred and Roth funds, so you could do your ladder of incremental conversions over time in one plan.The Solo 401(k) would also have the benefit of higher contributions, potentially as high as $56,000 in your age bracket, depending on income. 

Of course, I’d be using the equity I’ve gained in the current house so I wouldn’t have that anymore, but do not see any issues with the new builds appreciating as this is a rapidly growing area.I’m looking to discuss any pros/cons, faults, suggestions to this plan.

I have no turnkey providers that I have used to accumulate these properties and have $160,000.00 cash flow and pushing rents and increasing NOI rapidly and Cash Flow too.  

And finally, perhaps the more difficult question:How do you assess the value of a property in a rapidly appreciating area - an area that has been building momentum for over a decade, but has finally gained traction.

Time will tell, I am concerned our extreme government debt / Treasury bond issuance and the Fed Funds rate being held high for so long will begin to take a serious (and rapid all at once) toll on the economy sometime in 2024.

Some areas and deals may be eligible for tax increment financing, which will lower the taxes, but these are usually on the larger projects.

Intown areas are booming with apartment developments and a few areas are rapid redevelopment.  

Most attorneys, including the one that I work for, bill in either 10 or 15 minute increments.