Yes bad idea,
I've made hundreds of thousands of $$$ over the years using domains with the sponsors name in it. Slowly but surely over the years the sponsors changed names, went out of business or more commonly, demanded the domain name (then did nothing with it! Ouch!)
The best thing for you to do is spend that time building your own brand (own the twitter, facebook etc if u can).
You can still target the sponsor of your choice with your SEO skills, just that having the domain name in the url is bound to backfire eventually.
All those hours you spend on the domain name will eventually stop bringing you income. Build something you can own, control and will make you money for a lifetime
