I second Chris Mason 's response there in terms of you being able to qualify as long as nothing went south.It could very well be that the underwriter didn't know how to apply the fannie mae rules for calculating DTI with an investment property OR maybe their bank had an overlay.But basically, your DTI should not take a hit when adding that property.Here is how they're supposed to calculate DTI with an investment property.1) Figure your personal debt and income side.So lets say your monthly debt payments (i.e. car payment, credit cards, PITI on your primary residence, etc) are 2k/mo.

My question is:Is it advisable to use my credit card to pay for closing costs?

Open a separate checking account, get a debit card for it, put a chunk of money in for reserves and do all transactions from there.

So I increased the limits on my credit cards.

Once your paycheck is deposited put 25% directly into your savings or an account that DOES NOT have a debit card.

HELOC- This is like a credit card and the borrower can obtain a certain amount of money during the lifetime of the loan.

I recently learned about this really cool app that allows anyone, with a public library card, to download/checkout audio books, including real estate books.

Pays for the PITI of a 3.5% down FHA loan in a A-class area1 SFH rental that performs well1 SFH converted rental that isn't the greatestI can fund the $15k rehab with a 0% interest Credit Card that I can payoff easily before the 15 month term

Just keep all your other debts in check (credits cards, cars etc.) at it will go back up quickly. 

Without the credit cards debt, my credit scores is always in the high 700's.