At that time, my friend encouraged me to get into real estate with the idea of creating passive income and wealth in future (via appreciation).

Lost Income- normally 18 to 24 months. 

Velocity banking works by taking a huge 'chunk' and putting it down on principal, then paying down the HELOC with every penny of income you get. 

How much income do you need, and how much do you want?

Fake income documents are easily purchased online, and inexperienced screeners often miss red flags.

On a commercial asset the value is directly based on the NOI (net operating income).

Use tools like AirDNA or Mashvisor to provide market data on projected rental income and occupancy rates, and make sure your lender works with appraisers familiar with short-term rentals.

Meet with a local banker & schedule a time to talk with a mortgage broker, they'll give you at least a baseline of what kind of down payment options and rates are out there.After that, if you're still wanting to research more creative options, do some looking into seller financing (a very hot topic with good, and bad, advice out there), look into private lenders, and commercial financing options.If you're wanting to live in 1/4 of your quadplex, then conventional residential loans may in fact be your best option as you can purchase that with a fannie/freddy loan with very low down, and use up to 75% of the income from the property toward your own income. 

Both are for tracking income/expense and generate reports (P&L, cash flow, but not balance sheet) only, not for listing, screening, collecting rent. 

They generally treat the debt like they would with a rental and count around 75% of the gross mortgage payment as "income" in the DTI calculation.