A lot of great information here on credit card usage so I will add more because when I was building my first portfolio I used credit cards to buy and rehab homes.
1. When you have great credit and lots of income you can definitely get $100k cards. We currently have over $250k of available card credit.
2. How do you get the money off credit card? Once again when you have great credit and high available credit limits you will receive blank checks in the mail. We get at least 5 a week... they really want us to use the offers they send.
3. Yes! You will pay a transaction fee, anywhere from 0% to 3% with excellent credit. However I understand it can be higher for folks with not so good credit.
4. I have received offers from 6 to 18 months. Actually just got 2 in the mail today from USAA 0% for 15 months with a 3% transaction fee on 2 different cards.
5. Best cards offers we get are Discover cards, Citi bank and USAA in that order. Discover usually offers 0% for 18 months and 0% transaction fee.
6. We no longer use cards to buy houses because we are strictly A&B properties now. However we do still use them for rehab funds. It's hard to turn down free money and with 18 months to refinance a rehab it's little risk.