Are business cards a necessity being in REI?

Then again though, I had to turn in over 1200 pages of supporting documents for capital one for a credit card, which was declined, so who knows?

Only you get to stack the deck in your favor, you get to look at the dealers cards, and you get to decide if you want to play before you have to make your first bet.

Will I need to apply for many credit cards with my llc?

I have a few credit cards that have a large balance. 

You might find a guy with great credit but has a maxed out credit card so he will have a lousy score, or you could find someone who has only ever had 1 $500 credit card which he paid perfectly, so has a 750 score.

Needless to say we did it, and abracadabra on the 3rd day, we were able to afford our REI package.Yes, the ruse on raising credit card limits ends up being so that you can afford to pay for their course in full. 

Should be able to buy with less than $10k if they don't make you bring too much to the table and then you could front each $12k draw with credit cards,  your own money,  etc.  

One credit card is at 5,000, 0% APR, no interest until summer 2018.

I would throw all your extra money possible at the credit card debt first and completely eliminate it before investing in any real estate.