So, as the first property would be a triplex or fourplex, I was in the understanding that I could use 75% of the income coming from that initial owner occupied purchase towards my debt to income ratio going into the next purchase.  

Such short term rental  will follow these criteria(see numbered list below), in order to take advantage of (1) qualifying to fill out schedule E, thus avoiding the Self-Employment tax should there be any profits. and (2) being able to offset your W2 income should there be a paper loss. 

Assuming this is proper in your situation, with treatment of a tax partnership, reporting would be as such with a Form 1065 filed, claiming all rental income and expenses, and then issuance of a K-1. 

Your operating expenses appear to exclude property management, which can be 8-10% of your rental income.4.

I know that it is typically 20% gross income to have another company manage the property, but wanting to know the cost breakdown if I were to self manage.

I'm 25yo and motivated to grow my rental portfolio so I can replace my W2 income.

How is the rental income.

We advise landlords to require two main criteria:1) Household income should be at least 40x the monthly rent.2) Applicants must have a credit score of 680 or higher.It's also important to review credit reports for red flags like rental collections or high credit card balances.

That being said, you can use a primary home loan with rental income to subsidize it. 

Simply put, vacation rentals are investments, and their prices tend to be a certain multiple of annual earnings (rents).