Keep the domain, build content related to design and seo in your cityname.. use adsense or affiliates to earn. If you are building new sites this old site will help you get everything indexed.
If you are going to travel for six months sell it, the domain could lose some backlinks and ranking when you will ready to work on it again.
in case you are travelling sell out for 6 month or other option is ask some one to manage it for u, and share revenue with him, thats in case ur website is making good revenues.
I have the same situation, the only difference is my website is 6 years old and had the portfolio. I would not sell a site for $6000, if it can bring at least $500 monthly. Alex @ qesign.com