I agree with Peckish.....most of those kind of "loans" are just cash advances on the "new card". the rules are pay it off within the time frame and you are getting an interest free loan. BUT and the big BUT is even late payments of as little as one day can cancel the whole deal and you can be charged interest on the entire loan beginning at day one. I saw yesterday that some credit card companies are now charging 30% interest! Just be very careful and read the small print. And whatever you do, never even be late with a payment. And they don't care why you are late, even lost in the mail, you were in a coma, they do not care..
I bought my fancy pants sewing machine on one of those 48 months no interest credit deals thru the dealer and the fine print in that agreement was, if I was late even one day no matter where in the 48 months I was, the interest went back to the beginning and I would have to pay interest on the entire amount. To be sure I was never late, I set up all kinds of alarms, warnings and paid way in advance of the due date and followed up to make sure they got that payment before the due date. Managed to pay it off way early but it was stressful for me and I was glad to be rid of that obligation.
Good luck to you.
Murphy.