Connecting with a lender that can run numbers for projected mortgage payment vs  market rents in relation to the area you're looking into would be a good first step! 

When you are going to be living in one of the units you can use a low money down loan with a down payment of 3.5-5% down and live in the building for one year and then if you’ve saved enough for another down payment you can then put another 3.5-5% down on the next building and live there for a year and keep doing this year after year and build up a nice portfolio this way.

It depends on what your starting reserves are, but if you have enough for a down payment, I would look into DSCR loans for financing, as you can qualify based on the property's cash flow as opposed to your own personal income. 

Just to be clearer, I don't mean the method that tenants set up the autopay or Zelle in his bank account, but some method, app or digital platform, that debits the payment from tenant’s bank account at some specific date of each month, and It sends it to my bank account.

My rent is 3k a month and my payment is 4k a month.

@Michelle P Stafford, Any type of calculation of rent that includes a consideration of what principle they would have paid if they bought it, or corresponds to a payment amount of a loan could be considered an equitable interest in the real estate. 

Purchase Price: $380kTaxes/Insurance: $9,300 yearly (estimated)Downpayment: Up to $100kMy vision for the next 1-2 years is to live in the house and use the MIL suite income to pay most of the mortgage while saving enough for another down payment on another home that would become our primary residence.

If you don't have a ton of cash then NJ may be tough for you due to high price points (looking at 150k minimum for down payment and closing cost).

Our monthly payment with putting 5% down will be $6,700.

My monthly payment is 1,314 and the roommate pays 1k.