Such credit lines could be in the form of a credit card, gas card, or even a vehicle loan. It is important to service your debts responsibly and pay down you minimum balance do so can be building great credit. It often is good to have a co-signer for your first credit accounts that are established as begin to grow your profile on the credit rating scale. Lenders like to see a co-signer often times for your first few accounts so that they can have someone who is trustworthy.
Having a co-signer is a good thing and will indeed reduce the amount of interest that is charged on your begging debts to come. This is turn will decrease the payments that you'll need to make per month. This however can be a large responsibility and only should occur if the co-signer can fully have trust in you to service the debts.
When you show lenders you can handle any debts that have occurred, they will see you as a responsible borrower. This will be great in establishing a nice credit rating scale in the future to come.
It's very important to be aware of your credit profile when starting out because having several cards can harm your score if they're not used properly. Typically we'll recommend only having two to at most three lines at first. That way you can then take it slow and handle them well to build a nice credit rating scale in not time at all.