I have to register annually with the city I have property in (New Jwrsey) and have to pay a yearly fee for that and a separate annual fee for each rental unit.

I have family in the RGV and visit annually. 

@Shelly Shanks For buy and hold the formula is relatively simpleAnnually:(Monthly rent x 12)- property taxes - insurance -property management fees - HOA fees if applicable - budgeted maintenance and repairs- expected vacancy - loan payments.This will give you your annual cash flow. 

We've had the same tenants the last 18 months.Rent: $1,350/monthMortgage, Ins, taxes: $960/monthOur initial plan/goal was to acquire properties and hold them for long-term (20-30 years+) to essentially have the tenants pay for the mortgage and we would make a decent cash flow profit annually and then eventually have a solid asset (trying to diversify investing, e.g. not having everything in retirement accounts/stocks)Just recently the A/C had some leaks and is pretty much on it's last leg and needing a replacement (quote of ~$8-$9,000 installed + fixing leaks in duct work).

Do you pay out an annual percentage return (8-12%)?

(Part of this was timing since the existing lease was coming up on its expiration).2 - As others mentioned, make sure you understand the rules of the program and educate yourself ie. annual inspections are required, need to use the same lease terms as other properties, rent increases may need to be approved by the housing assistance administrator well in advance, etc.

Eventually you can buy it from them with potential seller financing option (to reduce their tax burden to a minimum on an annual basis. 

My numbers might be completely off (and this will likely be worth another discussion), but I need roughly 120 units, to cashflow an average of $150/mo to earn $220k annually.

I have been fielding offers for almost a year now and need to know how much revenue a 50,000 sq/ft self-storage facility in Hell's Kitchen would yield annually?

PMI for a conventional loan is roughly 1% the loan amount annually.