[Newbie] Cash vs Mortgage for Rental Property in Boston Area?

[Malvik Shah]

Here's my scenario I need your help with. I am looking to buy a 2 bedroom apartment for $450k. I have the cash to buy it. Is it wise to pay full cash or take a mortgage and pay 20% down and invest the rest in the stock market? What all should I be considering in making this decision? I could either live in this new apartment for a year and then rent it out or rent out from day 1 and find a rental apartment for myself to live in. 

If I paid full cash, my idea is to rent it out. Then save enough money and buy another apartment in 2/3 years with 20% down and use the rental income from 1st apartment to pay the mortgage for the second one. 

The other option is to buy two apartments for around $450k at 20% down and live in one and rent the other. When you buy a rental property, let's say the principal, interest, taxes, HOA plus everything else comes to $2000/mo. What is the minimum you'd rent it out for?

Thank you!