I don't get how someone can accumulate a large portfolio and not know this.

Seems a lot of future buy-and-hold investors start off with wholesaling as a means to accumulate their capital reserve

To calculate total accumulated cashflow, I calculate: income (+1.6% annually) - operating expenses (changing over time) - mortgage payments (constant).

But I'd like to hold on to the property, and any others I might accumulate, and rent to young professionals. 

Will be close to the area for the next 4-5 years and would like to accumulate 3-4 properties over the 1st few years of that time.

What is important is not to accumulate debt from one month to another, because they will never be able to catch up.If the 1st of the month is a Monday and the tenant is getting paid every Thursdays, then you might expect getting paid on Thursday, not a big deal for me.

I think the easiest way to accumulate properties with a limited budget is to buy an owner-occupied property, while looking at it as a future investment.

I work as a geotechnical engineer by day and am just starting to accumulate enough savings to jump into my first buy and hold deal.I have already read many topics at Bigger Pockets and am already using the 50 percent rule to make cursory analyses of properties in which I might be interested.

This will be the quickest way to accumulate rentals, as well as flips. 

If you accumulate an aggregate net operating income in the $50k range and place a mortgage on it for 80%ltv, you will achieve your goal and cash flow in the $2500 a month range.