Definitely a good move but 18 is still too young to marry. I married in my teens and was far too young, as was my husband. In those days no-one lived together before they got married, so marrying was the only way to be together. We divorced eventually and I met my lovely second DH, so all turned out well for me in the end. How much more sensible to give living together a try before marrying. Doesn't always work out, of course. I know a couple who were together for several years before marrying and split one year after the wedding. There are no guarantees!