I’d estimate it to fall between $200k and $400k.

Always recommend doing a soft-pull especially since not sure exactly when you'd find a property but you can get qualified and get some estimates.  

Estimated costs range from $500–$1,000 annually, depending on the complexity of their LLC and rental activity.For Partner 2 ($148K joint income, W-2, 1099 income, 1 rental, 2 kids), a CPA is strongly recommended.

Additionally, the estimate for my tax preparation for this year was approximately $1,000 over the cost I paid last year (including the time I paid for them to correct their errors).

Compare other rentals with a similar size, location and bedroom count to get an estimate of what the rent would be while you're living there.

Is $800k a good estimate (~ $73k door)?

Again i believe it is my best estimate of actual sustained maintenance/cap ex in my market.I did an estimate about 1,5 years ago on a emerald coast 3/2 condo with class a interior finishes and came up with $300 for just the interior (class a finishes cost more).  

I'd estimate your cash flow after you pay the loan payment would be $600-$800, which a lender that understands investment real estate should give you some credit for on your DTI.As for a bank, I have a specific lender at NBI that I would recommend.

The two existing LTR units (on my family’s property) were built 5–8 years ago at a cost of about $80,000 per unit, so I’m estimating a 20% increase in costs for the new builds.My plan is to use the equity in the land as the down payment for the construction loan, which I expect will make closing costs the primary upfront expense.

Also, make sure to connect with local contractors to get estimates on your prospect properties.