You essentially would be digging deep into your own pocket when these costs arise.

Ali,When planning to buy in NJ the biggest thing I would tell you is to plan/research for the closing costs.

There may be costs associated.

I figured the only holding costs will be the utilities. 

This creates two loan payments ($100,000 of equity and $300,000 on the new mortgage).Key NumbersHome Equity Loan Interest Rate: 6%Mortgage Interest Rate: 7%Rental Income: $3,000 per monthExpenses (management, taxes, insurance, maintenance): $800 per monthIncome and ExpensesMonthly Rental Income: $3,000Monthly Expenses: $800Monthly Mortgage Payment: $2,000ExplanationThe investor earns $3,000 in rent each month.They pay $2,000 on the investment property mortgage and $800 on other expenses.This leaves $200 profit each month or $2,400 per year.However, you have to pay $6,000 interest on the equity borrowed.This leaves you with an annual loss of $3,600.This example shows that while the rental property generates positive monthly income, the interest cost of borrowing the initial $100,000 results in an overall annual loss.

This strategy requires knowledge of local markets, renovation costs, and the ability to manage or oversee renovations.I am a loan officer and I could advise you on how to tap into that equity and put that money to work.

It helps accurately estimate the costs of purchasing, renovating, and selling a property, ensuring a clear understanding of potential returns.

Managers cost so much and make repairs cost even more, I do not see their value until you have 50+ units and no time. 

Can't recommend @Joseph Cornwell enough, he helped me buy my first duplex in Cincinnati and he has a contracting business, so he can give you advice on repairs, remodel costs, etc

Consult with a Financial Advisor: Seek advice to navigate negotiations and explore refinancing options that best fit your needs.By taking these steps, you can work towards lowering your interest costs while keeping your loan terms unchanged.