Since this is a real estate forum, I'd just clarify what someone could buy the real estate for and what your lease terms would be.How many sq ft?

Focus on analyzing properties and starting small, like house hacking or buying a single-family home to rent out rooms, while ensuring cash flow and maintaining an emergency fund.

This would likely take coordination with a tenant at some point - (ie - plenty of notice to them that they must vacate in order for you to sell the property)Since your current home is free and clear -  you could do a cash out refi or take out a new mortgage on the new house to be able to buy your paren't house and pay off the mortgage.  

My goal is to buy one rental per year with price between 150k-250k for the next ten years (if i get to keep my job). 

Buy your Aunt out first 

It sounds like you have a great background for investing as well as assisting other real estate investors in buying suitable real estate. 

I've helped people with SBA loans to purchase real estate for a business, but for buying rental real estate, the DSCR loan is a much better option.

i have people in my network who find deals; they get paid if I buy them; i diligence them; and then my PMs manage them.i didn't look at your profile, but do you already own rentals? 

Buy an existing house to live in and add an ADU in the back.

Yes you can buy stuff over the counter however as said most of it will be junk.