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.). 

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

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

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).

I paid tax on it and mowed it about every 5 years so maybe put 10k into over the years.. deductive reasoning suggested city does not build and full blown interchange to go to nowhere. 

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

I don’t have a loan on the property and hold it cash, but, if I sell it would lend the profits as hard money and earn 10%+. 

I put my money where my mouth is on this.We lend our own hard-earned money to local real estate investors.

Instead of evicting them, i was thinking is there some way that I could rent it back to him for very cheap (mainly to cover just the taxes/ insurance) ie 2k a year rather than the going rate of 2k a month for similar properties.

If you need financial help, ask under the "Finance, Tax, and Legal" forum.