Any credit card builds credit
With one exception (prepaid credit cards) – all credit cards build credit.
Secured credit cards, student credit cards, retailer’s credit card, store credit cards – they all build credit.
You need at least two years of timely payments to have a decent score. However; if you only have one account, your credit file will be too “thin”, and you may not qualify for large loans, especially a mortgage.
Mortgage lenders look at more than just your score. You will need a clean credit report (no delinquencies or other derogatory items) and sufficient activity on your report – at least 2 or 3 credit cards (try getting a store card) and at least one installment loan (either a student loan or a car loan).
When it comes to getting a mortgage approved, you will need to demonstrate a minimum of 2 years stable employment history, and sufficient income. These factors may have more weight on the lending decision than your credit score.
Hope this clears things for you.