I was told by a coworker who owns a property there and he says he has a management company who does everything and hands off and after all expenses are paid, he nets between 2000 to 2500 per month in Tampa FL. 

When eyeing multifamily investments, you’ll likely encounter two key metrics – cap rates and gross rent multipliers (GRM).At first glance, they seem similar, but there are some important differences between the two.The GRM simply divides the purchase price by the property’s total potential rental income–it doesn’t account for operating expenses.Cap rates, on the other hand, factor in both income AND expenses to give a more complete profitability picture.The main advantage of cap rates is their ability to evaluate better and compare investment returns, risks, and value.

I would really look at your expenses again and make sure your not upside down at the end of it.

The net operating income (all expenses + taxes + insurance) of 12k sounds about right if this is an all-cash deal, but if financing is required, which is 25% down + CapEx, that beautiful 12k operating income shrinks down to around to 1.5k operating income which translates into $125 of monthly cashflow, and this is what gives me the 4.5 CoC that I was talking about.

After having flipped half a dozen properties and using expensive hard money, I'd looking for another, cheaper, option. 

NJ is expensive, especially the taxes. 

Labor is less expensive and available, regs non existent, demand high, more fresh air year around versus enclosed,

Would 10% of the purchase price be fair if I feel that will cover expenses (485K purchase price asking)?

What to do if a tenant is wanting yearly pest control which can get expensive and the LL wants to simply handle a couple mice with setting traps.

I do not want to self manage this property, a manager at 40k/yr will be about a 30% expense to the noi after the value add project is stabilized.