I sold one earlier this year and essentially paid off all credit card debt. 

and am planning on doing another HH (4 - plex) when I can, I'm also looking to break into small mulit-family ((8 - 15) units) as my first "real" investment by raising private capital, both by the end of the year hopefully.My question is meant to start a conversation as I look at House Hacking as dipping your toe in the water prior to diving in, there is not much information on what to do between dipping your toe in and swimming... so, 1.)

If you don't agree with their criteria, ask if you can raise the standards on your property.

Unless you've had a credit card since you were 14 and the same job for the past year or two and some $$$ in the bank, I can't imagine they'd loan to someone so young (again maybe they won't even loan to anyone under 18). 

Planning to do minor renovations and raise rent by bringing in section 8 tenants

How would I go about getting my first credit card, and eventually moving into an American Express to inhabit the benefits of the cards?

Next, I paid off my credit card debt that had gone into collections.

The only reason to flip is to raise cash to actually invest in buy and hold deals.

What the real hidden secret of Lowes, if your a contractor, is don't fall for the idea that 0% APR for 6-months with a Lowes credit card is the best deal.

They simply raise taxes, which they will be doing real soon.