Long-term, I am interested in buy-hold rentals for passive income, becoming financially free, and also to build generational wealth.Currently, I have a pre-approval and actively looking in the North New Jersey area for a multifamily property for my first house hack.

Proof of Funds can be tricky if you don't already have a deal when you're applying for a pre approval. 

Hey, I was just wondering If I can open 2 0% APR credit cards and use the Cash option or check for 10-20k and use that cash for an investment property to flip?

I currently own and am living in a condo in a ski town in Colorado.

For example, if the loan is $100K @ 10% APR and 2 points, you put up $50K of the principal and get 4% APR and 0.50 points. 

I recently got a pre-approval from rocket mortgage for 250k with a 3.5% down payment.

Without a pre-existing relationship, the best you will likely get is a year, but you may be able to get six months or thereabout.

I would like to put in a full price offer on a studio near the ski area of Big Sky Resort in Montana within 24 hours.

Also i imagine an accepted offer should be followed by due diligence that allows for latest financial statements of the tenants as a pre-requisite

There are peak market rentals like ski resorts, beaches, etc that are kind of cool if you want to make a lot of money in season then occupy out of season.