The answer is very simple, you need to buy a domain if you are serious about your future business.
You can register a domain (.COM) for about $ 10 per year, but if you want something really good you have to look at the aftermarket. Prices range may vary from $ 50 to $ XXXXX for a single domain name. There is a popular markets such as Sado, Flippa, GoDaddy, Undeveloped and so on.
Think about the domains as an investment, a good .com, can bring you many site visitors, the domain price is more likely to rise in time .... think about your domain like about your online office ... if you are happy to rent an office for 1,000 euros per month at top spot why not spend money on top domain ....