The website industry is very competitive. Programmers from other countries are willing to undercut you at any price as their standard of living and wealth is much lower. They live as kings in their country for $6/hour.
If you are not already very good at design and coding, you are going to need to build your skills. Generally to start your portfolio you could offer a website that was poorly made to be redone for free with a link to your "design company/portfolio" and you build from there. If your website was good, people who visit the site may like the design and hire you.
As for building templates, it's not impossible, I don't mean to discourage you, but you would need a lot of knowledge in SEO. So many good designs are never seen because of lack in SEO/good domain. And once you get in the top 10 on google, your designs and custom website would have to be spectacular.
If I were doing it, I think it would take 2 years to get a top link for templates, but I don't think it's worth it as it's a declining market.