I have gutted to the studs the last 5 properties I have bought from tax/foreclosure sales in this county and this one is not far from a full rehab. 

This is obviously much better than $1,400 per month.On top of that, you will now get 2x the depreciation write-off so your taxes should go down.On top of that, you will now get 2x the appreciation when real estate price go up.On top of that, your tenants are helping you pay down the loan, initially at about $100/mo for both properties, which gradually gets better and better.On top of that, you now have more units so if one or two goes vacant, you have more renters covering the losses of the vacant units.If you want to keep these properties, I would do a cash-out refi and go buy more rental real estate.

Zero capital gain tax, next to zero income tax, property Tax is super small.  

To succeed, focus on properties in high-demand neighborhoods like Pecan Grove or Aliana, and ensure your cash flow analysis accounts for high property taxes, potential HOA restrictions, and flood insurance costs.

Texas is definitely a strong market, but keep in mind that high property taxes can eat into your cash flow.

I mainly want to ask if these assumptions are reasonable and if there's anything I haven't considered:(1) multifamily units in NJ close to New York City, ~$1,000,000, 20% down payment, (2) Using the following assumptions: 4% appreciation rate, 6.5% interest rate and 5.0% refinance after 5 years, $10,000 yearly maintenance fee(3) ~$6,000 monthly rental and assume 3% increase yearly with 5% vacancy rate(4) Based on the above, the calculated IRR if selling at the 10th year is ~19% (considering tax benefits) and ~17% (without tax benefits).

You'll want to put together a personal financial statement (basically lists of all your assets and liabilities) and have your tax returns ready.

And you would get to indefinitely defer all tax on the gain from the sale.

If you are taking out a conventional mortgage of any kind, you can't buy in the LLC as it does not have two years of tax returns.You are also asking if an entire state is good to buy multifamily, which means you are too soon in the process to even talk about buying.

Generally speaking, with SFR or small multis, I just rely on the lease/rent roll (and some form of proof of payment; i.e. bank statements, deposit receipts, tax returns, etc.).