In this business, access to readily available sources of cash allows investors to take advantage of opportunities to buy properties at below market prices the moment they are known. I've found that low-interest lines of unsecured credit are the most cost-effective source of short-term financing available today.
In the past I always immediately dismissed and shredded those 0% APR cash advance checks and snarled at the cc companies for their ever creative ways of ensnaring people into cc debt, but after seeing the interest rate charged to me on my Zecco margin account, I would happily take their 0% for a year and earn interest on their money.
But BEWARE. The cc companies still have ways of making their money. They charge fees for cash advances which may out way the benefit of the cash advance. Look for a capped fee of $30-$99, which is a good deal if your withdrawing large amounts. The majority of offers I'm seeing today for 0% cash advances come with a 3% fee, so if you with withdraw $10,000 your already down $300. Look for a capped fee and make sure the interest rate remains 0% after a cash advance is requested.
Taking advantage of your revolving credit and paying on time should increase your "credibility" with your creditors. With time, they will probably increase your limits (which you should request every six months) allowing you to use this new unsecured credit to quickly finance properties with the characteristics of a great investment.